Hello,
Thank you for your appreciation and for your question, it is something that has come up many times over the years.
The simple answer is that it is currently only possible to have 1 charset, 1 tile-set and 1 map.
We have thought about adding support for multiple maps many times over the years and while it would be theoretically possible, it also introduces many complications, for instance, currently each project has a single display mode, a single matrix colouring method and at least one common colour (ie. screen colour)...
If multiple map support were added, we would soon be asked to allow different display mode, colouring method etc for each map, some people would then not be happy that all maps have to use the same char-set or the same tile-set, so would request multiple support for those as well.
The point I am making is that any introduction of multiple maps, tile-sets or chars would almost certainly add enormous complexity to the program, opening a proverbial "can of worms".
In the end, we decided to just keep it simple, a lot of "multi-map" situations can be resolved by simply drawing all required maps into one big map and using the Flexi-grid feature to export the data for each sub-map separately if required.
Also, would you really want to use the same char-set on ie. all 16 levels of your game? that could be quite boring for the players (ok many classic 80's games did this!)
So I'm sorry if this answer is disappointing but I hope you see what I mean about the "can of worms" it could become, it's really not as simple as it may seem and there is usually an alternative route that can be taken.
Cheers.