Hi There. Yes, it is possible. Before I explain how this can be accomplished, first let me throw out the usual disclaimers and warnings that what I am sharing with you is unsupported as it is not an product feature to intended be used by customers. The code I am sharing with you is just an example. If you wish to use this code, you do so at your own risk blah blah blah blah blah 🙂
Now that that's out of the way, Yes -- you can bulk load items into private catalog so long as you have a good understanding of how Flexera curates Technopedia data and Technopedia in general, are willing to do the work to stream line your incoming data format and you have some experience writing SQL stored procedures.
Please see the attached gist links for sample code. Again, this is not supported and use at your own risk:
(example proc for creating releases)
(example proc for creating mfrs)