Main window not visible

I'm on my first steps in LibreCad and so far loving it. There is still a lot to discover, but my first drawing is like expected.
Yesterday I had the opportunity to work with a second screen. Sweet. But today I'm back on my laptop. But now I'm in trouble. When I start LibreCad it seems to be started, with ALT-F I can even open a file. However the main window seems to be stuck on the not existing second screen. I can't use LibreCad anymore.

So I deinstalled LibreCAD and moved now to 2.2-rc1. But still no main window. Seems that unless I buy a second screen I will not be able to use LibreCad again.

So where can I reset application settings to move it back to my primary screen.

Windows 10 -> expert
LibreCad 2.2.0-rc1 -> n00b

I tried: reinstallation, regedit, scanning AppData

Found a solution, sometimes coffee and a walk in the park with the dog helps.
For those that ever might face this on Windows:

Start LibreCAD
Minimize all open windows Win-M  (Win-Shift-M is maximize all)
Click on the taskbar icon of the open LibreCad

And voila: back in business

I used to use an app that had the same issue of being set to display on the second screen. The developer intended to ignore the setting if the second screen wasn't available but the solution was just to delete the config file and start again. Perhaps someone can identify where the config files are, and this setting is, in LibreCAD.

I added an issue on github for this: https://github.com/LibreCAD/LibreCAD/issues/1166

Also noted the config location for Windows there.
Deleting the config file will reset many other settings too, so this should be the last choice.