That would be groups of the same weapons in the game! Thanks
Groups of the same weapons? As in weapon pick ups? Just clarify for me, otherwise if your talking about units then:
Its quite easy. This works for grouping any units together as well. Select the unit group eg. F1 that has the units you want to move, then hold down Ctrl and press the unit group you want to merge the selected group into eg F5. This will then merge all units in the F1 group into the F5 group, therefore getting rid of the F1 group. Note that each group can only hold 10 units, so you cant merge 2 groups into 1 group if there is more than 10 units in total. So if F5 has 5 units and you are trying to merge F1 which has 7 units into F5, it wont work. What you would have to do then is select the F1 group, press the ~ key in the top left of the keyboard, select a single unit using numbers 0-9 and then Ctrl F5 to the F5 group, and do that with other single units until you have filled the F5 group.
Hope this helps