resetting layout does not work.There's topic for 2.3.4 bugs here: https://forum.yoyogames.com/index.php?threads/2-3-4-stable-release-thread.89092/ .
Try to reset layout from top menu.
I guess I will wait for a hotfix. Very disappointing since I finally have time to develop.So you probably need to install previous version as for now, and report a bug to YYG. They will for sure make a hotfix for this in few days, as I see more people got this issue.
After trying the beta it still doesn't work. I guess I'll have to be patient but I'm definitely worried about my project.You can try to install latest beta, it's working for me on Windows, maybe it's only stable which got some more fixes since last beta and have this issue - you can grab beta for Windows here: https://gms.yoyogames.com/ReleaseNotes-NuBeta.html .
I didn't checked stable yet, as seeing bugs like this I'm also waiting for hotfix already.
C:\Users\<USERNAME>\AppData\Roaming\GameMakerStudio2\yourname_xxxxxxx
C:\Users\<USERNAME>\AppData\Roaming\GameMakerStudio2\Cache
C:\Users\<USERNAME>\AppData\Local\GameMakerStudio2\GMS2TEMP