Like me, you have buttons at the bottom labelled "Open" and "Open in folder". Do these not work?

Double-clicking the required message also opens it for me.

I understand that I can open an email. But I want an email view pane so I can look at many quickly. Like I can do in the quick email search. I add file below. My suspicion is that this is not available in the main search function of Thunderbird. Is there any 3rd party way of searching Thunderbird emails with a 'file view' pane?

You're apparently not satisfied with the Global Search, which for all its poor specificity in defining a search, does allow reasonably good browsing of what it has found for you. And its "show email as list" option switches you back to a conventional view.

Where I know which folder I want to search in (as you presumably do since you're using a folder-centric search mode, I find the Expression Search/GMail UI add-on a very useful enhancement to the QuickFilter Bar, so much so that I haven't used ctrl+shift+f in years.

I think if you need or want to persist with the ctrl+shift+f search mode, you need to try the "save as search folder" button. It's a few more clicks but you will see your found messages collected together in a new (virtual) folder along with all the usual viewing tools. Just delete the saved search folder when you done with it, if you don't expect to use it again.

Thanks. I will try your suggestion.