3rd teams in active leagues

[Grenland]

So I am trying to make the Norwegian third division, almost everything works great. However, a couple of teams have their 3rd teams in active league (3rd division) - These 3rd teams are also actually their U19 teams.

The game can ble played and all, however, when managing one of these teams and I go to the "teamname U19" tab, I try to filter by U19 only - not possible, it cannot be ticked. The only selection that is visible is Reserves (2nd team) - When viewing this screen I see all the Reserves + U19 players.

Also, I noticed that you can select a league the highest a "2 team/reserves" can be promoted to, do that also applies to "3 teams/u19"?