Let me explain it a different way.
Dens graduate to the next rank as they graduate grade levels in elementary school.
Our dens are perpetual. The patch the Scout wears and is associated stays with him for all of his tenure in the Pack.
Den 5 as a Tiger will always be Den 5 the next year as a Wolf, etc…
In TroopTrack the promotion of the Den from Wolf to Bear then activates the next set of requirements and awards the Scout is capable of working on.
When a Scout is promoted to the next rank in TroopTrack - he then moves to that new Den.
When we were smaller - on den per rank - it wasn’t an issue. We just had them stepping stone from one rank to the next. The size of our pack now - 120 Cubs and 18 Dens - the logistic is more of a burden.