If possible please change subdomain as follows
In that case you can activate in Dev and Staging site without increasing site count. That means you can activate there for free.
Not only my plugin, Most of the plugins PRO version follow this rule. So this may apply for your other plugins PRO version also.
If you cannot change subdomain then no need to activate in softgrid.app.vedagrace…. This plugin will work without activating also in Dev site.