my problem looks like that:
-| Parent Channel (pass)
---| sub1
---| sub2
As you see there is 1 parent channel which IS password protected and 2 sub-channels which are without password.

I would like to do following thing:
-> User who will join "Parent channel" will now be able to join all sub-channels in this channel.

Sollution I tried:
I set needed_join_power 65 for sub1 and sub2. And I set join_power 65 for Parent channel. It didn't work. BUT when I make group which grants 65 join_power and I will grant this group in "parent channel" then this trick will work.

But... default group is "Guest", this channel would have hundreds of users and I don't want to assign to all of them groups manually.

Waiting for your sollutions