SUMMARY
I tried to import a CSV, it failed with a red bar at the top:
  [ERR-5]: Import of file named '/path/to/file.csv' failed
and the same message in the Messages panel. This doesn't identify the problem.
I went to all the trouble of setting `export SKGTRACE=10` and reviewing the trace output and then realized I could click the [History] button at the top before it goes away to see the missing actual error as well as the failure summary:
  [ERR-5]: Columns date and amount not found. Set import parameters in settings (Configure Skrooge... / Import/Export / CSV / Edit regular expressions...).
and then this secondary message does appear in the Messages panel.

I don't fully understand what's happening but it seems both messages should appear in the transient top panel and in the Messages panel without having to click on a [History] button that goes away after a few seconds.

STEPS TO REPRODUCE
1. Find a bad CSV file
2. File > Import > Import...

OBSERVED RESULT
You only see Skrooge's final report of import failure, not the message about the actual problem that caused the problem.

EXPECTED RESULT
Show all Skrooge's messages about the import, not just the last one. I guess if there were dozens of messages the transient top bar might overflow, but it seems there's enough room to display two messages, and an indicator '^...[more]...^' if there are more. Maybe this [more] could be a button replacing [History].
I don't see why the Messages panel doesn't show all messages, without having to click the transient [History] button.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: n/a
KDE Frameworks Version: 5.69.0
Qt Version: Qt 5.14.2 (built against 5.14.2) , on xcb

ADDITIONAL INFORMATION