Hello, Al,

Thank you for your request. Currently, we do not have in our plans implementing JSON tagger. However, if we receive more requests from our clients we could consider it. 

Note, RadSyntaxEditor offers a convenient mechanism for creating a custom tagger. To do so, you can inherit from the abstract generic TaggerBase class. The abstract GetTags method is responsible for acquiring all spans of tags that meet a specific condition.

A sample approach is demonstrated in the following help article: https://docs.telerik.com/devtools/winforms/controls/syntax-editor/features/taggers/custom-taggers 

I hope this information helps. Let me know if you have other questions.

Regards,
Nadya
Progress Telerik