Loading saved meshes and variables

hello… i need help on the idea of having the player build walls/objects in the level.
then save all of the objects and their locations in a savegame class…

for example: player assembled a 4x4 square room with table and chair in it. ( lets call this ROOM X )

so then when everything is saved… player then plays the game and starts at ROOM A…

i was wondering if it is possible to load room x connecting to a door of ROOM A.

or load / connect any other room … ( ROOM B / ROOM C / ROOM D etc… )

any idea how?

i got the saving objects and locations in a savegame class…

but the loading part not so…

as seen at the attached image…
Rooms B C Z etc are already premade…
and are loadable to connect with room A