I managed to fix the problem, thanks to these two threads! The problem was fixed by uninstalling a windows update with a version number close to the ones described here, which were impacting Edge Webview 2, MX studio uses that for several elements such as the design mode, the micro/nanoflows screen, several parts of the UI...
https://community.mendix.com/link/spaces/studio-pro/questions/144616
https://stackoverflow.com/questions/79790827/localhost-applications-failing-after-installing-2025-10-cumulative-update-for-w
If anyone else is having a problem with tabs such as design mode, micro/nanoflows, toolbox, etc, then do investigate this, maybe you have some problem or a faulty instalation of this dependency.
Edit: is there any way to mark my own reply as the successful answer???
Hey Matheus,
Give it a try, please, on another laptop / PC. Try to understand if there's an issue with your device or not. It could be either the device or the operating system or something weird on your device interfering with it!
This sometimes happens due to a temporary rendering glitch in Studio Pro. In many cases, simply closing Studio Pro completely and reopening it fixes the issue.
If that doesn’t help, restarting the machine usually resolves it as well.
Upon further inspection, the problem is specific to 'design' mode, structure mode seems to work alright, which narrows it down