Create a copy while the list is available
Open My List and choose Create backup. Copy all the generated text into a note or document you control. The text describes recognized titles and episode checkpoints; it contains no film download. Keep the complete text intact so that it can be read when you need it.
Merge in the receiving browser
Open My List on the other browser, paste the text into Restore backup and choose Merge backup. New recognized titles are added. Missing checkpoints can be added too, while any checkpoint already saved in that browser is kept. Read the result message to see how many entries were added or skipped.
If the backup is rejected
Check that you copied the entire text and did not replace punctuation while editing it. A backup from another product is not necessarily in the same format. Unknown titles are not guessed into unrelated entries. Keep the original note while checking the source list, so that a failed attempt does not cost you the only remaining copy.
Make a newer backup after important changes, especially before clearing browser data or replacing a device. You decide where the text is stored and who can read it. The tool does not send your list to a social account or recover a historical website login.