Your Macs.
See which Macs use your Showglass Pro key, and free one when you move to a new Mac. The key and the email are in the purchase email from Dodo Payments.
Find your license
Showglass Pro
Deactivating a Mac frees its place. Showglass on that Mac goes back to the free previews until you activate it again; nothing on it is deleted.
The key and the email are checked with Dodo Payments and never stored, logged or put in the address.