When using Folio I typically don't like to bid on notes for loans that I already am invested in. In the past I would open up the original Prosper listing for everything I was bidding on and see if the yellow banner appeared letting me know if I had already invested on the loan or not. Lately this banner has not been appearing correctly for me and I accidently picked up a couple duplicates.
Since I am not the only one who doesn't like picking up duplicates I decided to save myself the effort of even needing to look at the original Prosper listings by adding a new Folio specific search filter to remove any loan that I have already invested in. The new search option is "Folio Exclude Screen Name". You can put any lender's screen name into this field and any loans that lender help fund will be excluded from the results. Currently I don't have access to any information about notes bought/sold on Folio, so this won't prevent you from buying the same note on Folio twice, but it can help prevent you from buying duplicates of notes you picked up at origination.