How does template_ID_preview actually work?

Could someone explain to me how template_ID_preview actually works? The documentation seems a bit cryptic to me. What can I put in “data=” and “property=”? Can I put custom data, for exaple a few selected brushes instead of all of them? Thanks

Hello, have you found the answer to your queston ?
If so, i’m really interested in it… i haven’t found much things about it…