Is there a way to disable able the left mouse move in the viewport?
Hello there @mookfasa!
Checking around the community, as far as I could find, the left mouse input for moving in viewport is built into UE’s navigation, and cannot be directly toggled. However, what you can do, is alter the camera flight controls.
To do so, go to Edit > Editor Preferences > Level Editor > Viewports, and locate the “Flight Camera Control Type”. There, you can switch it to “Use WASD for Camera Controls”, which will allow you to move around without tne need to input any mouse keys.
I know this is not the exact change you were asking about, but it’s the closest we can get with the current UE build.