International management - adding & removing players from squads

I want to manage some of the nations in the World Cup, but I want to use the same squads that have been announced for the tournament IRL.

When I go to remove players from the international squad and add those that I want, either the "add player to squad" button doesn't do anything or isn't there at all. Also, removing players from the national squad doesn't seem to work either. Adding and removing them from the national pool does nothing.

I'm new to international management so would someone enlighten me if I'm doing something wrong?

the best  way is to use FMRTE you can swap players in/out of a national squad at any time

So you wait until the squads are named then change as necessary otherwise you will have to have multiple human managers added in game to try and pick the exact squads