Can we add a filter in card manager: IS NOT ON BOARD
Solved
Card Manager question
Best answer by Mary Houston
Thanks for posting
Are you looking for filtering for a particular Board or are you generally looking for cards not on a board?
If you want to be able to filter for cards that are not on a specific board, I would suggest posting this as feedback in the Product Feedback section. If you are generally looking for Cards that are not on any Board, you can use the below filter in Card Manager:

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