I realized that the subheading of the listing (to be seen under the location name when clicking on the map or looking at the list of properties) is key to get into the categories.
Categorized listings have the name of a lake or a national park here. Then it sais "Near XXXX" under the location fo the listing. In the attached screendump it sais "Near Laguna Dulce", which is the name of a lake. It it is on the lake category!
BUT: Where does the subheading come from?
I cannot find it anywhere in the listings or in the 'edit' part of my listing...
Any idea where this subheading comes from?