Could you add 'search text' function to the websocket tab?
So I've created this fiddler script to search within websocket messages... it adds a column and logging to report where the string is found
Fiddler script to search within websocket messages (github.com)
A fine suggestion. The workaround today is to select all of the WebSocket messages in the list, then click the "Inspect as Response" button to move them to the Web Sessions list as faux responses. You can then use Fiddler's normal Search features.