In reply to Herb Miller.

It's easy if the themes share font and color slugs. For example, I used the tool to test X3P0 - Reflections (my theme) as the parent and Avant-Garde as the child/style. Colors were broken in many places, sometimes generating white text on a white background. Font sizes, particularly when defined in patterns, were not set because they exist in the parent but not the child theme.json in use.

It's easy to move theme.json files from one theme to the next, but it is a broken experience at the moment because of the non-existent standards for slug-naming.

My theme is a simple one-pager. It's easy enough to fix the inconsistencies. But, as block themes become more complex, the problems multiply.

Side note about the generation tool: the generator adds templateParts and customTemplates to the theme.json if they are registered in the child, even when those template do not exist in the parent. Right now, the HTML template files are not included at all.

Also, that's a pretty awesome tool.