ID:134283
 
That can probably be done by manually editing the dmp, but how about an option in the map editor to combine several dmps together (to different z levels, just as if you've compiled the game with them separate), with an added option to export the current displayed z level to another (new or exiting) dmp.
I'm fairly certain this is why we have things like:

hub://LummoxJR.SwapMaps <-- .sav or .txt maps
hub://Popisfizzy.pif_mapLoader <--- .dmp maps

That said, I doubt it'll be implemented when it's already been done and it's easier for them.
In response to Audeuro
True, but I think he means to do this in Dream Maker itself, instead of having to load up those, just having a button in Dream Maker would be fairly easier and quicker.
In response to John Doh
Then my point stands even more-so. They added the Select and Ctrl + X, Ctrl + C, Ctrl + V functionality. What more could you ask for?
In response to Audeuro
Heh, a Ctrl + E to export the current z level to a new map file, and Ctrl + I to import a map file into the current map file? :-) Less work.

But yes, I know, I'm lazy.
In response to Audeuro
Yeah, John Doe got it right. Actually, you should've too; I did mention "Map Editor" twice.
This could be pretty useful and MUCH easier than having to load projects to parse the dmp etc. Doubt it will take much time to implement, as well.