Describe the bug
Icons in the toolbar should not have separators between each of them. Separators should only appear if there are more than two icons present in a feature or addon (i.e., like the Zoom feature).
To Reproduce
Steps to reproduce the behavior:
Expected behavior
There shouldn't be separators here:

or here

But I think they are nice to have, at least it is clear to me what kind of add-on are grouped...?!
Each icon already represents discrete functionality - they don't need to be further separated from other icons to achieve that.
So they end up occupying more horizontal space yet don't communicating anything new.
This is fixed?
Yowza!! I just released https://github.com/storybooks/storybook/releases/tag/v5.0.0-rc.5 containing PR #5711 that references this issue. Upgrade today to try it out!
Because it's a pre-release you can find it on the @next NPM tag.
Closing this issue. Please re-open if you think there's still more to do.