That's the first I've seen with something like this and I don't really remember how I locked in my environment setting. It looks like you've got a cloud account so I doubt it's that.

I think medibang has a tendency to lock certain panels to one side or another so I'm not sure if thats it but the only thing i can think to suggest would be to mess around with the environment settings or maybe check the window tab and see if anything can be toggled there.

An option to save your workspace/environment settings like clip would be nice but I've no idea if they'd add something like that.

Still hope you manage to find a solution