I encountered the same issue and was able to find a workaround.
Unlock Windows 10 taskbar.
Turn on all other panels so you could see an empty Taskbar Monitor pane.
Right click on a (right in my case) separator next to the empty Taskbar Monitor pane -> View -> Large icons
Now if you right click on an empty Taskbar Monitor pane you can access context menu and launch main window with settings.
This a serious issue and needs to be addressed if anyone keeps supporting this app.
Maybe somewhere the program leaves a settings config besides the program folder itself? Windows 10.