As I said:
You can start with this forum search on the HTML Prompt tag:
I have used a system called "Text Tags", which is simply the tag name (one word) proceeded by an "@" symbol.
Here's an example:
Using MACRO: Spotlight Search Prompt by @DanThomas, initially I see a window like this:
I can then filter the list using my "Text Tags", like "@strings"
Of course, this requires that you do both pre- and post- processing to get the actual item that is selected.
I see no reason that this could not also work with the KM Prompt With List action.
Does this help?