how does one find words with special characters in help page searches e.d List-ID

Are you asking how search on the website works or is your question about Thunderbird?

sorry not clear. It's on he web site

e.g https://support.mozilla.org/en-US/kb/new-thunderbird-desktop

Matt, perhaps more sensible if I ask about the reason for my search. There is an element in the header of emails from a particular sender labelled List-ID with a value e.g List-ID <spc.46828.0.sparkpostmail.com> I wondered; what is it? and can it be suppressed as it enlarges the header section unnecessarily?