How to export or read style data from Keynote or Pages?

I do a lot of work in Keynote, but I need to do other work in other applications (Affinity Designer, Sigma, etc). When I have style data (particularly gradients, and shapes) in Keynote I would like to be able to use it without all the manual work currently involved. I decompressed the package .key and now have .iwa files. There is one called DocumentStylesheet. But I can't open it. I've even tried all those stupid websites that say they can convert it. Please help!