How _exactly_ is a modify.dkim block defined in maddy.conf?

[mcgrue]

I've tried several variations on modify.dkim {...} and modify { dkim ... } as per the docs at https://github.com/foxcpp/maddy/blob/master/docs/reference/modifiers/dkim.md and I keep getting:

unknown module or global directive: modify
or
Unused configuration block at /etc/maddy/maddy.conf:186 - modify.dkim (modify.dkim)

What am I doing wrong here? (I just want to set newkey_algo ed25519. the default key is too big for Route53's TXT records ;_;)

[mcgrue]

I see. It's:

submission {
    modify {
        dkim { ...

Am I wrong that https://github.com/foxcpp/maddy/blob/master/docs/reference/modifiers/dkim.md isn't referenced on the website, though? I had to discover it by searching through the code on github.

[foxcpp]

Here it is: https://maddy.email/reference/modifiers/dkim/, named "DKIM signing" in sidebar.