How to Add Letter Headers for Table Frame

[Amala]

I'm working on a street index in ArcGIS Pro using a table frame from a street layer, that's sorted alphabetically. I’ve set up "Label" and "Page" columns and want to add headers above each group of labels based on their starting character (ex.  "A" for labels starting with A).

[JesseWickizer]

Add extra features to the street layer that only have individual letters for their "Label" attribute and nothing in their "Page" attribute. These records will be included in the table frame, sorted at the beginning of each new letter.

To edit the style of these letters to stand out from the other labels in the index, first add a new "Label_Sort" field to hold the sort order of the table frame. Populate it with the contents of the "Label" attribute.

Next, use text formatting tags to manipulate the style of these letters in the "Label" field such as adding bold or italics or adjusting the alignment. 

Since the text formatting tags change the sort order of the table frame, change the table frame to sort by the "Label_Sort" field. 

Table frame with letter headers: