How to lock the view to the XY, XZ, or YZ plane When I'm in top, bottom or side view, I would like to lock the view to the 2 dimensions of the viewing plane (XY plane, XZ plane or YZ plane), so that - when working in that view - I don't accidentally turn the view into 3 dimensions. How can this be done?
There's the Toggle Quad View option, which has such functionality.
It splits your viewport into multiple views, that cannot be rotated.

View > Area > Toggle Quad View
Shortcut: Ctrl + Alt + Q