the icon for get variant (selection screen variant) is actually Shift+F5
F4 is the usual search help which only works for a field where your cursor is located.
I guess you are talking about the field Display Variant, which is the ALV variant for the result list that can be chosen in the lower part of MB52, this is not a selection variant.
You only get to see general variants and your own personal variants, you can't see other users personal variants