AwesomeButton
Proud owner of BG 3: Day of Swen's Tentacle
When you select an army which is in position to exchange units with another one, the "Exchange" button appears next to every army garrisoning a settlement, even if it can't exchange units.
Crusader Army IV can exchange units with Chief Ageboya, so selecting either of those two will display the button with two arrows, but it will also be displayed next to Crusader Army V, which can't really exchange units. Clicking the button next to Crusader Army V will instead open the interface to exchange units between Crusader Army IV and Chief Ageboya.
Also, I was able to open Crusader Army V's interface, drag a unit and drop it outside the window. Somehow this unit showed up in my "Reinforcements" army, which is some movement points away from Drezen, where the source army (Crusader Army V) resides :D
Crusader Army IV can exchange units with Chief Ageboya, so selecting either of those two will display the button with two arrows, but it will also be displayed next to Crusader Army V, which can't really exchange units. Clicking the button next to Crusader Army V will instead open the interface to exchange units between Crusader Army IV and Chief Ageboya.
Also, I was able to open Crusader Army V's interface, drag a unit and drop it outside the window. Somehow this unit showed up in my "Reinforcements" army, which is some movement points away from Drezen, where the source army (Crusader Army V) resides :D