Customization of left panel

[mrk-z]

It'd be great to be able to customize the composition of the left panel with different tabs. For example, combine multiple tabs into one so that they are displayed at the same time, or change the order of the tabs, etc.

Currently, we sometimes need to switch between the tabs very frequently (mostly between Text and Sources, or between Sources and Reference Font), and it quickly becomes a lot of extra clicking and switching back and forth when we need to perform similar actions to a lot of glyphs.

I think the ultimate goal would be to have a fully customizable panel (we talked about maybe something like InDesign?). In the meantime, if there are other functions that could be added to reduce the amount of switching between tabs, that would also be very helpful.

(For example, the ability to edit text string directly in the canvas #566 so that we don't need to switch to the Text tab all the time; or maybe linking a reference font to a certain layer/global weight, so the reference font automatically changes when switching sources.)