Describe the project you are working on:
Space Tactical RPG https://twitter.com/ZeroPointGame
Describe the problem or limitation you are having in your project:
This proposal is part of a much more complete UI/UX overhaul and should be considered with this view about Godot Editor problems and possible solutions: #1503

Godot has multiple panels each one for a specific task. With the current modular position system you can choose 8 positions that better serves you for each panel. Godot 4 makes it even better with floating panels. It's very useful for multi monitor users (mostly of us right?) since you can detach a panel and send it to another monitor. But there's some big problem here. For some reason you can't detach, change, add or remove the panels from the bottom and up elements. Also you can't detach or change position of the most important panel that would make usage of multi monitors, the Script one. This is related to two UI/UX principles: Flexibility and Consistency.
2a. Provide choice in methods of use.
3b. Be consistent with user expectations and intuition.
Describe the feature / enhancement and how it helps to overcome the problem or limitation:
Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:
This is partially covered here in a smaller scope. https://github.com/godotengine/godot-proposals/issues/28
Bottom and Left Panels
Unify the Panel behavior making all just tabs with the same behavior. So they can be changed position to other docks freely and can be detached as well. Obvious some panels don't quite fit every position well, there's two approaches to it. First you can just let the user do what they want (Blender and Visual Studio approach) and if it's ugly to have the inspector in the Bottom it's ok because they can just change it anyway and it will not be default. There's also a more conservative approach that would be to have a list of allowed docks that way each panel can be attached but i'm not on it, i really would prefer the full customized way. Game developers are power users, let us have agency about our screen setup.
Top Panels
The Top Panel is challenging not only it don't have a clear meaning (2D and 3D are viewport options, script and Asset Library are other panels) but they also require huge screen space to work. Also as noted before the most important detached panel is not currently detached and it's the Script Editor. This is so much important to multiple monitor users to be ignored. So my suggestion to the top panel is:
2D and 3D should be unified in a single "Viewport item". After that a option to this "Viewpot Mode" (2D/3D) need to be added.. It need be accessible all the time in viewport so should be a fixed option in the viewport top header.
Asset Library should be a floating panel by default. Just like a File Browser. It's not used so often that justify it own option here. It can be hidden in the Project menu e.g
So it let us with 2 functions Viewport and Script. What makes sense here is to keep Viewport fixed and Script as any other Panel, i mean, you should be able to put the script editor in any dock and be detachable too. I can quite think in some screen setups that would work just great with the Script in the left dock. Again the point is that Users should be allowed agency about their screen setup everytime it's feasible. With max flexibility users can fix bad default UI decisions, make it more pleasant or more similar to what they are used to.
How the default screen would look like:

How complex sub panels in bottom would look like:

If this enhancement will not be used often, can it be worked around with a few lines of script?:
Will be used Often
Is there a reason why this should be core and not an add-on in the asset library?:
It's a core editor feature.
2D and 3D should be unified in a single "Viewport item".
I think it is a bad idea. Those who only need 2D will find it inconvenient to work with 3D in the background.
Asset Library should be a floating panel by default. Just like a File Browser. It's not used so often that justify it own option here.
Here you may be right. On the other hand, a separate tab can be seen as promoting the Asset Library.
I think it is a bad idea. Those who only need 2D will find it inconvenient to work with 3D in the background.
If you look at the mock-up, the 2D/3D split is still there, but the buttons are on the toolbar.
a separate tab can be seen as promoting the Asset Library.
I never used AssedLibrary for any of my projects, so if someone doesn't use it, they won't use it. We could just indicate that AssetLibrary exists, by doing something like #1499

The current editor theme is not intended for sub-tabs.
The current editor theme is not intended for sub-tabs.
What the problem with sub-tabs? Tested it here and it work better than my concept.

What the problem with sub-tabs?
They just look ugly. The problem is not with the sub tabs, the problem is with the theme.
I will also make a proposal for the default theme soon 馃槅
The theme itself is good, but it is not meant for sub-tabs. I tried to improve the picture in Paint.
Before:

After:

But it seems to me that the current bottom panel design is good anyway, without sub-tabs.
But it seems to me that the current bottom panel design is good anyway, without sub-tabs.
@dalexeev Much better your version but see that the proposal is not about subtabs in bottom panel. It's just a very small consequence of a much more flexible and unified panel dock system. Only posted this sample because it was fair to show how complex elements would work on this proposal. But the proposal itself is not about it.
Not only this would be comfortable for working with laptops or any small screens in general but it also makes the workspace looks a lot cleaner for big monitors
let us have agency about our screen setup
I concur. My preferred setup would be viewport on the far left, and then 3 columns of panels: File System, Scene, Inspector (this way I would have to drag stuff across the whole screen over the viewport).
That's impossible to do in the current design since there can be max 2 column on either side of the viewport currently.
Also you can't detach or change position of the most important panel that would make usage of multi monitors, the Script one.
The ability to detach main screen plugins is something that will likely be implemented by itself anyway regardless of any UI overhaul, it just hasn't been done yet by anyone. This would include the ability to detach Script to its own window.
(2D and 3D are viewport options, script and Asset Library are other panels)
No, 2D and 3D are completely separate things in Godot, they aren't "viewport options". It's not like in Unity where 2D is "flat 3D".
Asset Library should be a floating panel by default. Just like a File Browser. It's not used so often that justify it own option here.
If you are using the Asset Library, you don't need to view the 2D/3D/Script main screens at the same time. Having the Asset Library be its own main screen makes sense to me. I don't think it should be a dock like FileSystem.
The ability to detach main screen plugins is something that will likely be implemented by itself anyway regardless of any UI overhaul, it just hasn't been done yet by anyone. This would include the ability to detach Script to its own window.
It's good news but i highly doubt it will be implemented by itself if no one code it. 馃榿
Since there's no public roadmap for UI changes is impossible to know about what will or not be done. So here's my proposal.
No, 2D and 3D are completely separate things in Godot, they aren't "viewport options". It's not like in Unity where 2D is "flat 3D".
Not by the user point of view (which is the point here right?). They are exactly views for the 2D and 3D parts of your scene. If they run in different engines and physics... there's not diference for the UI/UX perspective. It's so transparent and used as a Viewport option to the user that it even changes automatically when you select a Node of the 2D or 3D type... If it was a 2D/3D switch in the header as proposed (Check the croqui) would change nothing the current design and workflow.
If you are using the Asset Library, you don't need to view the 2D/3D/Script main screens at the same time. Having the Asset Library be its own main screen makes sense to me. I don't think it should be a dock like FileSystem.
If you're using the Asset Library you need to view nothing about your current scene, you're just really in a (bad) browser searching for a asset to download. It's a totally standalone tool and used so little often that have no point in keep it up there. I can see no better place than a floating window if you want to keep things coherent.
Most helpful comment
If you look at the mock-up, the 2D/3D split is still there, but the buttons are on the toolbar.
I never used AssedLibrary for any of my projects, so if someone doesn't use it, they won't use it. We could just indicate that AssetLibrary exists, by doing something like #1499