Bug 444888

SUMMARY
KMail 5.18.1 (missing from Version list as of writing). Invitations for recurring events with specific exclusions only show the days-of-the-week of those exclusions, not their dates.

OBSERVED RESULT
For example, when I view one invitation message, I see this on the "Recurrence" line:
"Recurs weekly on Fri. until 2021-12-17 10:00 A.M. (excluding Fri.,Fri.)"
Notice the "(excluding Fri.,Fri.)" part. Now, in this case I know this refers to two specific dates in the past where this recurring event was cancelled. But only the days of the week are shown, so it could easily be confused: Is an exclusion in the future (as a user might reasonably assume) or the past? Is it recurring or once-off?

EXPECTED RESULT
My thoughts:
1. Exclusions should be differentiated and displayed with better clarity. Weekly recurring exclusions can be shown as generalized day-of-week, but specific exclusions should be shown as specific dates.
2. There may not be a need to display exclusions for past dates. But perhaps some users find that useful. Could have a "Show past exclusions" button/link which shows them, or perhaps a config option somewhere.

ADDITIONAL INFORMATION
I also just noticed that if I click the vertical sidebar that says "Calendar Message", it changes between "Plain Message" and "HTML Message" - but won't switch back to "Calendar Message". I have to change the current email to get back there.