Creating Youth team leagues, and lower leagues populated with B teams.

[gunnaragusts]

I've been recreating the Icelandic league so it plays over the winter and has 20 teams per league. I also wanted to create an U19 league structure comprised of three divisions with teams in the first second or third division depending on what division the main team is in. But I wanted to then make the leagues independent of the main leagues so teams could be relegated and promoted indepently of what division the main teams are in. The problem is even though I have created three leagues with U19 divisions as their type, I dont know how to populate them with the U19 teams that are created in the "Reserve teams to create" tab in advanced rules . I know that it's possible to create youth leagues using the "Reserve teams to create" tab, I essentially just want to add relegation and promotion. 

Secondly I would like to make three lower division populated with B teams from teams in the top three divisions, or at least one division with b teams from the top division teams. I know I can take teams and just turn them into B teams but I would like to know if it was possible to get the editor to create B teams under the "Reserve teams to create" tab in advanced rules and then populate a league with those teams. I essentially want to create a similar system as the one in spain where B teams can be playing in any division lower than the main clubs division.

Any help would be very appreciated, I've been trying to figure this out for the last two days.