How to create variables in-game?

This is a unique thing to ask but basically, I'm trying to create permanent variables in-game as opposed to in-engine.

I'm making this RTS game and I want to the player to create as many squads of units as they want.

I have a "squad" struct that stores the array of units. I need to be able to create more arrays in-game. I'm pretty sure its possible but I'm having some trouble. Any help would be awesome