Mike,
Thanks, good question.
On the Structure Board, you can select any issue and Fix the widget on
it. In terms of your example, what you need is select the Parent Issue
and use pin icon to switch to Fixed View on that issue.
On the issue page, technically we could do the same. However, we
decided to allow Fixed View there only on the issue being viewed, so
the pin icon works slightly differently. The idea is that when you
view an issue, you need to see what it's part of (the parents) and
what it consists of (the sub-issues).
I can see the benefit of fixing the view on some parent issue, such as
in your case - however, it must be carefully thought through to avoid
confusing everyone about how it works. There are multiple use cases -
the user navigates back and forward, changes current structure, and so
on. I don't think fixing the view on an arbitrary issue - like it's
done on the Structure Board - would work.
If you have any ideas about how the UI for selecting the target issue
of the fixed view could look like, or what would be other related
cases, please share.
Kind regards,
Igor