You can see which samples are in use the global->samples->view ram
Here’s a screen shot of my sample ram and the ones not in use have an # in front of their sample size, in this case the first two samples listed. (Se picture below)
There isn’t however any “unload unused” in the AR but that would be a really great feature indeed.
Workaround is to go trough the ram view and manually select unused samples by pressing the yes/save button and then select unload in the right side menu.