So I use the option to restore sessions, because I use tons of windows in my work, and arrange them manually based on a specific logic. This used to work 99% of the time... until I got a second screen.

Ever since I have two screens my windows just get maximized vertically every single time I log into Plasma. It doesn't matter if I manually size them before logging out.

I tried to set a Window rule with the desired dimensions, but it won't work either. "Set initially" and "Remember" does nothing, "Set now" and "Force temporarily" resizes it for now but it will be back to the wrong size again the next login. The only way I found to have them the size I want them is "Force", but that then stops me from manually resizing them so it's not a real solution.

As an aside, also have several other issues since I have two screens, eg. lot of windows, programs, popups will always open on my secondary screen which is to the left off the main (that's where I had space for it) instead of my primary screen.

Arch Linux, up to date
Plasma 5.17.5
Dual screen set up with xrandr.

I wonder if it would help to reset the desktop session:

• In System Settings > Window Management > Window Rules, clear out any window or application rules you set up to try and work around the issues.
• In System Settings > Startup and Shutdown > Desktop Session, change On Login to Start with an empty session.
• Log out and log back in. This should open a blank session so you'll need to reopen your applications.
• Go back in and change the On Login back to Restore previous session.
• Set up your windows just the way you like again.
• Log out and log back in to confirm.