Been plying for 60+ hours with only a single rune socketed on each item, because I cannot for the life of me get the cursor to snap to the 'empty rune slot' menu (in the individual items), as it just jumps straight to the runes themselves.
I managed to attach 2 in the bottom left inventory item, as the cursor was already over the selection menu.
I hope someone has an answer - I'm frustrated as hell.