Normally, in networked multiplayer, when a unit levels while it is not that player's turn who controls this unit, the advancement dialog is skipped even if there are more than one choices available.
This mod works around this by providing a right-click menu usable previously to leveling while it is that player's turn. Only the host needs to have downloaded this mod.
This modification is supposed to be compatible (and makes sense) in combination with all kinds of 'standard wesnoth' scenarios, eras and modifications; or in other words, with everything where units can level to two or more other units.
Requires BfW 1.11.10 or greater.