I might be looking on a wrong source, but is here an endpoint for Youtube where I can list what scopes did the user approved? (This way I can make it so he needs to approve them if he is performing an action that he denied/revoked).
This is not possible there is no api that returns information about what scopes a user has granted
Autothizarion servers can return claims in their access tokens, refresh token, and or Id token. Sometimes this information contains the scopes granted. This depends highly on the authorization server setup. Googles doesn't return that. Your best bet is going to be to make the request and then request additional scopes if it fails