When choosing an option to split formation, create a subgroup within a formation instead of assigning them to a new one. So for example:
I have a group of archers. I can choose them by pressing 2. After I split them, I create two subgroups within that formation. So to pick each subgroup I'd have to press either 2, then 1 (picking first half of archers) or 2, then 2 (picking second half of archers) in a quick succession.
I think it's clearer and more easily manageable than assigning them to an arbitrary different group, e.g. skirmishers or heavy cavalry, like it works currently.
I have a group of archers. I can choose them by pressing 2. After I split them, I create two subgroups within that formation. So to pick each subgroup I'd have to press either 2, then 1 (picking first half of archers) or 2, then 2 (picking second half of archers) in a quick succession.
I think it's clearer and more easily manageable than assigning them to an arbitrary different group, e.g. skirmishers or heavy cavalry, like it works currently.