I was hoping you could help me with the following:
If you select multiple gameObjects, you can use the move/rotate/scale-tools to chance their Transform values simultaneously as if they were one gameObject from within the scene-view.
However, when I tried to input exact numbers into the inspector, only the last selected object would change. Is there a way to change the location/rotation/scale-values numerically instead of using the scene view?
I know this isn't exactly what you're asking for, but you can move them all into container object and move that where you need it. Everything inside will move accordingly.
You cannot modify multiple Game Objects via the inspector (in any way) at the same time, you can only, as you have already discovered, drag them around the world.
You can write an editor script to do it. Shouldn't be that hard either.
It can even be an editor window right under the inspector that looks and feels exactly like the real deal if you really want something like that and it's important for your day to day work.