Units can be organized into custom formations, however this doesn't always work. Especially with artillary the unit order is often changed:
- Arrange the unit cards in the right order.
- Form the units into a group.
- The order is changed to what I'll call the 'background' order.
- Force a different order by dragging a unit card and dropping it on the group to move it to the end. If you do this in the right order, you can force the order.
- Now the unit card order is respected.
- When moving the units around the card order is not respected, instead the background order is used.
- When the grouping is removed, the unit cards revert to the background order and abandon the forced order, which is what normally does happen.
Again, in most cases I can form a custom order and send units into battle respecting that order. This problem seems to occur when artillary is mixed with infantry. Here's a screenshot of this happening with a group of two bolt-throwers, White Lions of Chrace and Lothern Sea Guards. My custom order is:
Sea - Lion - Bolt - Bolt - Lion - Sea
The order when I click and move the units around is:
Bolt - Bolt - Sea - Lion - Lion - Sea
So it seems the artillary is pulled out, while otherwise the order is respected.