Allow rearrangement of UI elements

[claell]

Is your suggestion for improvement related to a problem? Please describe.
From Visual Studio Code (and other applications), I am used to easy rearrangement of UI elements, ideally by drag and drop. This would be a nice feature, especially for large screens. Personally, I am mostly thinking about the entry editor, which for me would probably be more usable on the right (compared to below the entries). This is how I know it from Citavi.

Describe the solution you'd like
As written above, drag and drop rearrangement, possibly also some adjustments of the UI of the rearranged items.

Additional context

[claell]

Entry editor on the right might be especially useful in combination with #6857.

[ThiloteE]

• Requires discussion about UI, general concept of UI and potential effects on other UI components
• Requires checking if compatible and doable with JavaFX
• Warning: NOT "good first issue" (at least not yet at this point in time)

[koppor]

This would IMHO lead to a complete rewrite of the JabRef UI. Brave persons could look into Eclipse RCP.

Other UI frameworks seem to be outdated (see the links at https://stackoverflow.com/a/2381696/873282) or not that flexible (Jetbrains IDE) or web based (that's what we are aiming for with JabRef-online).

[claell]

Actually, web based might not be that bad, if you look at VS Code for example. It can be executed both locally and in a web browser. That way, development efforts of JabRef and JabRef-online could be shared. However, I assume that it currently might not be an ideal decision and that other frameworks are favorable.