Hi!
I don't use favicons/site icons so I have them turned off in about:config. And they also happen to be a privacy risk. So I always have them off.
Regular tabs in Firefox give me back the space that's normally used for those but I can't seem to get back the space in TST. Please help.
Thanks :)

No more empty favicon circles. And that space should be used for the tab's name instead. Like here with regular tabs.
Empty favicon circles.
TST Options => Advanced => Extra style rules like following should do that:
tab-item:not(.faviconized):not(.loading) tab-favicon {
display: none;
}
Thank you @piroor :)

But is there some way to move the text further towards the left edge?
@barkoder you might want to check the instructions on how to inspect the CSS in the sidebar. (https://github.com/piroor/treestyletab/wiki/How-to-inspect-tree-of-tabs) From there you can see all the effective CSS and find what works for you.
In your case, you can simply change the tab label margin to 0 to get back a little space. You can go further left, but you have to remember there are twisties shown when there is a tree. The CSS might be too generic for your solution, but might give you an idea.
tab-item tab-label {
margin-left: 0;
}
Thanks @irvinm that did move the text a little futher left. But is there some way to remove the twisties completely and move the text all the way over to the left? I always double click the tree's parent to expand and collapse anyway so I don't need the twisties.
tab-item tab-twisty {
display: none;
}
Thanks @irvinm finally the text's all the way left.