Add File System dock side-by-side visualization

[samdze]

Describe the project you are working on:
2D platformer, 2D top view, ect. but applies to every project.

Describe how this feature / enhancement will help your project:
A new mode, featuring a side-by-side view of the File System dock would allow for much more space being utilized effectively by the dock itself in every type of project if a user decides to give the dock more width than default, making it possible to display two full-height columns of folders and files.

Show a mock up screenshots/video or a flow diagram explaining how your proposal will work:
Unity already does this way:

Describe implementation detail for your proposal (in code), if possible:
I guess utilizing a HSplitContainer instead of a VSplitContainer and moving other UI accordingly could be enough.

If this enhancement will not be used often, can it be worked around with a few lines of script?:
No, this is one of the editor's main features.

Is there a reason why this should be core and not an add-on in the asset library?:
This is an editor improvement that potentially benefits every project.

[fire]

This is the closest I can get Godot to go.

Perhaps you can scribble on it with your changes.

[samdze]

Yes that's the standard "one over the other" view mode.
Shouldn't be complex to add this additional side-by-side layout.

[YuriSizov]

I'll close this proposal, as there doesn't seem to be a lot of traction for this specific idea. However, do note that the idea of utilizing space more efficiently for the FileSystem dock is still considered. We have #4565 to discuss more global changes of the layout (though it will have to wait post-4.0).