Enable Search in long messages opened through the "view entire message" pop up

When I receive a very long email (more than 100k characters), I cannot search in the whole email because P3 only shows 100k characters.

While I can click on the "view entire message" to open the whole email in a pop up, Search is not enabled on this pop up (I cannot press "CTRL+F" to search in it)

=> I would like Search to be enabled in the pop up windows, so that I can press CTRL+F and navigate through the matches