Take your bathroom scene and remove any characters, animation or scene logic from it. Anything you don't want in the final scene. Then save it under a new name.
Take your bedroom sceen and remove all parts of the enviroment. Every object in VaM is an "atom", so it can be removed. Note that many scene creators choose to "hide" atoms that belong to the environment so they don't get in the way when animating characters and setting up scene logic. Also be careful to not remove anything that might be related to scene logic, e.g. check if it has plugins on it, etc. Depending on the scene complexitiy you may want to go step by step and confirrm the scene still functions correctly and save a backup. Once you removed all you could, and the scene still functions, save your scene under a new name.
Saving both scene is important, so you can recover in case stuff goes wrong!
With the new environment-less "bedroom" scene open, now merge-load your cleaned up bathroom scene onto it. Merge-load is a button in the main menu, it combines two scenes.
If everything works, you are good to go. However, it might be that characters end up in collision with the new environment, as positions are different, etc. That might cause your characters to "explode". If that happens, reload from your backup and disable collisions on all characters before doing the merge-load. Then move either the characters or the enviroment to avoid the collision before you re-enable the collision. Note that some animation might be setup in ways can't handle moving the characters, in that case you need to move the environment instead (or change the animation).
What you have to keep in mind of course is that scenes would often be tied very closely to an environment. Poses and animations of characters would be matching objects in the scene, etc. Say characters in "lying on a bed" pose won't be easily fitted to a "sitting in bathtub" pose. Adjusting animations can be a LOT of work....you might have to redo them entirely. And animations are often 60-70% of the work, you might not gain that much by transplating the environment as described above.
