It's not so much a problem for me, but I've seen players with 50+ lions who have to name each lion in a specific way just to keep track of them all. It would be cool if we could create categories, give them names like 'SELL' or 'BREED' or 'MUT WATCH', and sort lions into them through the lion's page. The categories could show up in trade and transfer lists as well, and they could be collapsible there.

Maybe the categories would be in separate boxes in the Den, or maybe they would just sort the lion list into appropriate sections. It would be useful for players who like to give rankings to their lions, too.