Redesign UI
The UI can be messy and hard to maintain. UI components like the TileSelector is intrusive. It should be a popup window instead of being stuck to the current webpage.
I agree with you. Showing the tilemap all the time is not the best way to handle that. Something like that is already planned. It should look like the views and toolbars tab from tiled
Basically you select the windows you want to see and your selection is saved for the next time you use the editor. Also there could be shortcuts to toggle views on or off or switch complete workspaces.
Ever tried doing something like Paint.NET does?
I have no idea if this works, or is a good idea at all. Just making a suggestion.

That's where I would like to see the map editor head towards in terms of the UI.
The tile selector was implemented in #15. We should consider closing this issue
The features are not implemented. We could split this into multiple issues because this one has quite a few new features