Can i add my custom user field to a user mail template? [duplicate]

I added a custom user field (/admin/config/people/accounts/fields) with machine name field_about_user to my D9.5 site (yes i know, it needs updating...).

Now i tried to add that field to the Mail template Admin (user awaiting approval)by guessing: [user:field_about_user]But that's obviously wrong.

Do i have access to other variables than the default ones described in the help text at all?If so, how?

EDIT:From this question i understand that yes, there are some more. But only variables (=tokens?) of type user and system.

Now what's not clear to me is:

1. I don't see the mentioned Browse tokens link. Would that added by the token module that i don't have? Or is it just not available in D9.5?
2. As i can't browse for the Token: Would a token for my field be of type user? Or some other type? If it's available in user, how does it look given above field name? Is a token for it available via core tokens, or do i need the token module?