I too spend enormous amounts of time pouring through hundreds of Storyblocks items, marked my favorites in various ways (color tag, notes, title change) but have only been marginally successful in finding them again. I had sincerely hoped that I could ask to show just the BLUE tagged items, but that's not an option. My next best guess was to use the sorting options, so if I sort by color tag, I would expect to see all the blue tagged items grouped together either at the top or bottom of the list, but this did not occur. Likewise, I added an unique keyword in the Notes for all my favorites and searched for that string, but it didn't find them. Next I tried changing the titles but couldn't find them that way.
Sorry for the rant, but I guess that the bottom line is that the text search and sort features still need work.
One method that I have found successful in just general searching for "the perfect song" is to go to the Storyblocks.com web site. Even though I don't have a subscription (to the site) outside of LumaFusion, it still allows me to use their on-line search tools and quickly audition the tracks. Then, once I know the name I can usually search for the title back inside of LumaFusion. I should very much like to thank AudioBlocks for allowing this!