Make the copy before you need it
Open My List and choose Create backup. The text box contains your supported saved title identifiers and episode checkpoints. Copy all of it, including the opening and closing braces, and keep it somewhere you can reach from the other browser. It is text, not a movie file or a copy of another service’s account.
Merge into the other browser
Open My List in the destination browser, paste the complete text into Restore backup and choose Merge backup. The tool adds supported saved choices. Existing checkpoints in the destination are kept, so an older copied reminder does not replace a newer one that is already there.
Read the result
The result tells you what was added or skipped. Entries that do not belong to this catalog or contain invalid episode information are not treated as successful imports. If the text is incomplete or not a GStream list backup, correct the source text rather than removing random parts until it passes.
Saved choices do not synchronize automatically across devices. A private session, cleared site data or a different browser can explain an empty list. Backing up before clearing data is the reliable order. Return to My List to create or merge a copy.