No, since v4.14.3, no extra action is needed if you want to use Maps Marker Pro also on a subdomain. The only preerquisite is, that you activated your license on your main domain first.
If you activated your license on a subdomain first, please follow the tutorial on how to transfer a license to a new domain – once finished, activate your license key on your main domain first (like www.mydomain.com) and you will be able to use Maps Marker Pro on subdomains (like staging.mydomain.com) afterwards too automatically.