“Skill” or “Skills” is far too general; any developed talent is a skill.
“Gamer Skill” or “Gaming Skill” would seem to be more what the OP has identified. But gaming skill is only relevant within a game or game-like context, so perhaps “Game-Like” would be a more useful tag. The set of manga to which this would apply would not be a subset nor superset of that to which “Isekai” applied.