Save file in already played family.

helena26cake​  Yes, you can save the household and the lot to your library so you can install them in a new or another save.  But they won't be exactly the same as they are in your current save.  You have to save the household and lot separately for starters so the sims will lose their connection to all collectibles that you have out for display in the house. Anything stored in containers (fridge, chests, bookcases, flower and elixir workstations, etc.) will disappear as all will be emptied.  Many photos will be solid black, and you'll have to make new ones and the ones that don't turn black will also lose the connection to the sims that took them.  And probably a few other things.  The sims will lose connections with all other sims outside of the household.  That includes club and organization memberships.  Otherwise, the sims will retain all their skills, traits, aspiration progress, family relationships, and household funds.  They will lose all recycler bits and pieces and Batuu units.  And probably a few more minor things that I can't think of atm.

Hope this helps.