Creating custom render tokens for Cinema 4D is very simple with Python. First you want to loop through tokens and check that there is no duplicates.

if __name__=="__main__":
    for registeredToken in c4d.modules.tokensystem.GetAllTokenEntries():
        if registeredToken.get("_token") in ["my_token"]:
            exit()

Next you register your custom token with following command:

c4d.plugins.RegisterToken("my_token", "Comment", "Example value", MyFunction)

Last but not least you need the function that returns some kind of string that the token outputs:

def MyFunction(data):
    return "myString" # Replace this with your more advanced script

Here is my collection of custom tokens that might be useful.
Tokens included:

• Date Year Full (2021) – Token: $YYYY
• Date Year Short (21) – Token: $YY
• Date Month (01) – Token: $MM
• Date Day (16) – Token: $DD
• Date Hour (18) – Token: $hh
• Date Minute (42) – Token: $mm
• Date Second (10) – Token: $ss
• PC Name (String) – Token: $pcname
• Username (String) – Token: $pcuser
• Render Engine (Redshift) – Token: $renderer

Place the folder in the zip file to Cinema 4D’s plug-in folder.
ar_tokens.zip