How to change the default domain/path for ADDON DOMAIN?

Hi,
I don’t know why, when I try to add an ADD DOMAIN, by default I get a domain/path that is not the one I intend to use: how can I change it?

Don’t know if you are still looking for an fix to this… The workaround solution is to create a dedicated user (as reseller not admin) and set it as owner of the website of the main domain. Then log in as this user to add the addon domain.