Linking Maps RPG style

[PrisonLove]

Hello,

I was wondering if there was a way to link maps together akin to the way it is done in Bonus campaign from WC3:TFT (The one where you control the beast master)

If you can do this, how do you also carry a unit between the maps.

I don't need a super detailed answer, just the basic concept and maybe some specific functions/data items that need to be used.

Thanks.