Hey, thank you for your questions! :) The app generates the hex map and the dungeon maps randomly. Currently there is no import feature for maps planned, but I am thinking about implementing an editor to customize or generate hex maps manually inside the app.
As of now, you can change biomes and points of interest of a generated map, or details of already generated settlements, by editing the campaign files directly in the campaign folder. (Everything is saved as plain text Markdown or JSON)
You can also customize the random generation by editing or importing the random tables used for hex map, settlement, dungeon or NPC generation.
Since the goal of the app is to remain a clean "theatre of the mind" experience, there will not be icons or detailed tiles for the hex map or dungeon maps.