Created attachment 120463 [details]
on the left the workspace before restarting (right column's width was increased) and on the right after restarting (positions loaded their sizes not)

SUMMARY
Dockers have their positions saved but not their size (width, height), so if you start Krita, adjust sizes of dockers then close Krita and start it again the dockesr will retain only their position not transformation (size) and will shrink to the smallest width/height possible depeding on wheter it's a horizontal or vertical docker.

It's possible to do it manually, after restarting Krita (point 4. below), go to Window - Workspace - Select your new workspace, it remembers the positions and most importantly the sizes as well.

STEPS TO REPRODUCE
1. Open Krita
2. Adjust your workspace as yo usee fit (for example bring one docker to half the screen width or height wise - height for horizontal dockers, width for vertical dockers)
3. Save the workspace through Window - Workspace - New Workspace...
4. Restart Krita

OBSERVED RESULT
Dockers retain their position but not width and/or height, their size is set to the smallest possible.

EXPECTED RESULT
Workspace being the same as when it was saved, so position, width and height of all dockers (UI elements) to be stored and loaded everytime the workspace is loaded (Krita started).

SOFTWARE/OS VERSIONS
Windows: 10
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION
In the attachement you can see on the left the workspace before restarting (right column's width was increased) and on the right after restarting (positions loaded their sizes not). It's one of the default workspaces but it's the same with a new Workspace you create on your own.