I am sure there is a simple answer, but ive been trying for hours to Join/Merge/Connect/Glue/Combine Primitves together that are touching each other on the edges and to form a new, single primitve out of them.

In the pciture you see 13 surfaces (or primitives?) that i want to combine to only one surface.
I Tried with the "Join" sop, but it only gives me white borders no matter what i click
Any help will be greatly appreciated!

first Fuse SOP to make sure all your prims are connected
then Divide SOP and check Remove Shared Edges

It worked, thx! Not very intuitive though

Eastwood
It worked, thx! Not very intuitive though

For intuitive, try the dissolve tool.

Select the edges you want to remove, then hit 'delete' to dissolve the edges.

if you want one node which is an OTL anyway try the lab "extract silhouette" trace axis Y