Ah, alright, found the image replace function. (For future readers: Open the smart image, click on the tools-icon or hit F7, then use "clear image". This keeps the pin positions and you are able to choose another image. The image doesn't have to have the same size, but it is aligned to the upper left, so if you change the size the pin positions might be misaligned).
Example for 4):
My world has the following structure:
World -> Contintents -> Regions -> Subregions -> Hexes
I have a
map for the world, for
several regions and a big hexmap for a single region. On the big world map, I have pins for all the regions. But I would like to have a topic in the continent description, pointing towards the big world map (best would be, to have it focus on a certain region of that map).