Too many in this forum, e.g. Is it possible to hide a custom view if the query result is empty?
Depending on your requirements, there is a variety of possible configurations. Although it is possible to parse the block’s content or even its html, it is better to get the block’s id, then use Logseq’s API to read its properties from the database.
I don’t think that Logseq distinguishes properties by their origin. :block-hidden-properties should work for any custom property.
It gets a little philosophical. Could even consider providing multiple approaches and let the user choose one.