Can't find Tile Map reference in BP

Hi,
I would like to generate the static mesh of my map out of tilemaps. Since UE4 provides a functionality to create tilemaps with Paper2D, I would prefer it to external solutions like Tiled.
The generation of the mesh is written in C++ and I would just like to create a BP in which I can select a tilemap asset which is used to generate the map geometry in the construction script.
The c++ method needs a layer of the tilemap to operate on but I couldn’t find a way in the BP editor to set the simple tilemap (so not actor or component, just the asset) as a variable which I could get the layer from.
Is it just not possible to access the pure assets without placing them as actors in the map or as a subcomponent?
Thanks in advance!