Tell Me How To Play Any Group of YouTube Videos in a Row (Playlists)

I want to be able to choose any set of videos in a You Tube channel, keep the list and play all of the videos in a row whenever I want.

Will it work for all channels?

Is there more way than one to do this? How many ways?

Does it include shorts?

I want to start with these channels:

SyberMath
SyberMath2
mathgist3706
mathsmood
999kviewsmagictricktutoria6

I am also having a problem - my list of subscrptions has disappeared?