On the page https://dev.liferay.com/develop/tutorials/-/knowledge_base/7-0/importing-resources-with-a-theme there are some examples of sitemap.json and assets.json.
Unfortunately, not all use-cases are covered there. Some examples :
How to set Asset Tag to filter by certain tags?
How to set certain portlet preferences?
How to set priority on an imported web contents ?
Java API skills are needed to check in the code if setting certain values is possible and what values shall be exactly specified in the 2 aforementioned files.
It would be advisable to provide full examples of sitemap.json and assets.json showing what values can be set and exactly how, specifying which JSON value:property pairs.
Thanks since now !