it is very hard to select any association. I have to zoom in and right-click at the blue small square. When I right-click on the association somewhere in the middle the context menu is related to the diagram which I find quite useless. Reproducible: Always
Note that although the association apparently IS selected since all edges are highlighted blue, the wrong context menu is shown.
same with git master
To be able to see more informations about how AssociationLine selection works, it may help to enable AssociationLine debug (press Crtl-D and select AssociationLine). With debugging enabled I can see that pressing left mouse button inside the green bounds the association is enabled and immediatly disabled.
This is a problem specific to the 2.10 branch. In 2.11 and later selecting association at 40 % zoom level works as expected.