How can I request additional permissions for a GitHub App?

I have a GitHub app which has an OAuth client/secret too, but when I try to request additional permissions for the OAuth client it just shows the normal App permission request screen, without the additional permissions, which means I’m unable to get the additional permissions.

I have a workaround for this which is registering a second OAuth app and requesting the additional permissions through that, but it feels really messy.

Is there a better known workaround for this, and/or is it on the roadmap as a supported feature?