In https://metacpan.org/pod/Dancer2::Config  I see plugins should

have their configuration in

plugins:

   plugin-name:

       key: value

but I have not found any suggestion where should one put the application-specific configuration options.

Is there a recommended, or required hierarchy for those configuration values?

Maybe:

Oh an I think it would be also good, to add an example to that pod, showing how to fetch configuration values:

config->{appdir}

and

config->{applications}{'App::Name'}{key}