User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:97.0) Gecko/20100101 Firefox/97.0

Steps to reproduce:

Read part way though a long message, look at another, go back ...

Actual results:

... now back at the beginning. This applies to 'local' and tabbed views.

Expected results:

View should be preserved, so that cross-checking, for example, does not lose the place. For 'newsletter' kinds of message, which can be rather long, it is not possible to resume where one leaves off, it has to be hunted by scrolling every time. It is really annoying.
It looks as though messages in tabs are reloaded from scratch every time rather than being held in memory. The view pane might not suit such a place marker approach, but tabs surely must preserve the view.

Dr B W Darvell, this happens as you described - sorry for the inconvenience! We're fixing this in bug 545666 / bug 1729379, for which the comment below applies, because the proper fix for this entails complex changes quite deep in the internals of Thunderbird. The good news is, the proper fix will fix it once and for all.

(In reply to Magnus Melin [:mkmelin] from bug 487386 comment #96)

This is actively being worked on in other bugs for re-working how the 3pane functions. The fix will be in the 2023 release, and available only preffed off for Thunderbird 102 this year (since you'll have to accept rough edges if you enable it).

Thanks for the comment. I imagined it could be quite complicated - but not as much as it appears now! (Sorry I did not find the others of the kind.)
Still, glad it is in hand - I just have to be patient ...
Thanks again.

(In reply to Thomas D. (:thomas8) from comment #1)

Dr B W Darvell, this happens as you described - sorry for the inconvenience! We're fixing this in bug 545666 / bug 1729379

Not bug 545666, I actually meant bug 1729379.

Bug 1729379 - [meta] Implement 3-pane tab in a separate document
Bug 1729384 - Create message pane as a separate document (implement about:message)

OK, thanks.