When either swapping to different slugcats for players 2-4 on expedition OR using Change Player 1 in Expedition, only vanilla + DLC slugcats are selectable, and custom slugbase slugcats are skipped over.
Currently a workaround is possible for players 2-4 via first selecting the custom slugcats in the Story menu's slugcat select and then going back to Expedition, but that is not possible for Player 1, even with Change Player 1 in Expedition installed and enabled due to Expedition automatically swapping your slugcat to the campaign appropriate one whenever expedition is opened or an expedition campaign is selected.
When either swapping to different slugcats for players 2-4 on expedition OR using Change Player 1 in Expedition, only vanilla + DLC slugcats are selectable, and custom slugbase slugcats are skipped over.
Currently a workaround is possible for players 2-4 via first selecting the custom slugcats in the Story menu's slugcat select and then going back to Expedition, but that is not possible for Player 1, even with Change Player 1 in Expedition installed and enabled due to Expedition automatically swapping your slugcat to the campaign appropriate one whenever expedition is opened or an expedition campaign is selected.