How do I make multiple focus trees for one tag?

So,

My idea was that there is supposed to be an initial reconstruction-esque focus tree, which would culminate in the final focus triggering an event chain, which depending on choices made, would lead to specific second main focus tree (two different ones - one for non-aligned path, and one for fascism).

How does one achieve this? More specifically, how to I make this "second" focus tree and what tag do I assign to it, and what to put in the final event button so it switches to the second tree.

Best regards, Sincerely,
SeaTray