Quick Shortcuts for Rotation

Hey unity devs!
I've got a quick question to ask:

So, in my game, the platforms are all in a 3d sphere, so if I have to place a platform, I have to use rotation snapping to move it around the globe.
The problem is, I only want to rotate using the x and z axis, but the y axis keeps changing from 0. How do I only rotate on X and Z axis in editor in snapping? Any recommendations, even plugins would be more than helpful!

Thanks!