Custom formatting for legend headers in a Web Map / Web Mapping Application / ExB?

[ACCDVermont]

I am curious if there is a way to format the legend heading text (i.e. bold, underline, new line, etc.) of a web map. There doesn't seem to be any way to do so within the ArcGIS Online Web Map Viewer. I have also tried editing the JSON of a non-production version web map item within ArcGIS Online Assistant but no luck (shown below). Are there other avenues to accomplish this? Is it possible to make the edits happen in the Web Mapping Application side of things rather than the Web Map Viewer side? I am trying to see if it is actually possible and if it is possible, is the effort to accomplish it actually worth it.

JSON edits that did not work:

     HTML:

          <strong>text to be bolded here</strong> 

          <b>text to be bolded here</b> 

     Markdown syntax: 

          **text to be bolded here**  

     Using a style key:

          "heading": "text to be bolded here",

          "style" : "bold",  

JSON code snippet I am trying to edit in AGO Assistant:

View from the Layer Style Options tab in Web Map Viewer:

View from the Legend tab in Web Map Veiwer:

Thanks, 

ACCDVermont

[RussRoberts · Accepted solution]

This is currently not possible in Map Viewer to style that text displayed in the legend.