Pretty much as Aweu already explained.
If you only download maps the export folder is the place you need to clean out, it's just to delete the .fhm files with the map name that you wish to get rid off, the .obj files can be deleted if you know which ones that belongs to which map, but if unsure you can always leave them if you reinstall the map again or if other maps use the same object groups.
But if you made a map yourself and exported it you'd have portals to the map at two places since exported maps work pretty much the same same way as a map folder inside of the "FeralHeart/media/terrains" folder. The only difference is that the exported files are encrypted and consist out of less files. If you still wish to save a map you have but still want to get rid of the portals in cape, just remove the exported version of the map, then go into the map maker and uncheck the "has portal" and just save it.
This way you will still have the maps if you want to edit them in the future or use them again.
