Making Capital Only units

[Edi]

Clearing national recruitment list is not necessary.

You need to modify a start site (or create a new one), subject to the 5 trait limitation mentioned above and use the #homecom command for commanders and #homemon command for regular cap-only units.

If you need to reset the recruitment list, #clearrec is the command you're looking for. It's just not needed here. Check the 3.26 modding manual and specifically site modding, as well as the recruitment lists section.