Your system information

• Steam client version (build number or date): 1707518866
• Distribution (e.g. Ubuntu): Arch
• Opted into Steam client beta?: [Yes/No] Yes
• Have you checked for system updates?: [Yes/No] Yes
• Steam Logs: steam-logs.tar.gz
• GPU: Nvidia/Intel/AMD Intel hd 3000
• Desktop Environment: KDE Plasma 5.27 X11

Please describe your issue in as much detail as possible:

Describe what you expected should happen and what did happen. Please link any large code pastes as a Github Gist

If you maximize the Steam window via its maximize button, then minimize it and restore it, it will be in an unmaximized state.
This works as expected on Steam stable channel.

Steps for reproducing this issue:

1. Open main steam window
2. Maximize window via maximize button
3. Minimize window via minimize button
4. Restore window via taskbar

Observed result: window is not maximized, state is lost
Expected result: window is maximized, state is as before