SUMMARY

Moving thousand of files with Dolphin freezes Plasma Shell

STEPS TO REPRODUCE
1. in any directory, create 10 000 files (with a simple "for i in {1..10000}; do touch $i; done"
2. open this directory in Dolphin
3. create a subdirectory
4. cut / paste 5 000 of those 10 000 files into this subdirectory

OBSERVED RESULT

The whole Plasma Shell freeze indefinitely. I have to kill & restart the plasmashell process.

The usual "(i)" appearing in the system tray / widget when a file operation is performed to indicate its completion level does not appear.

EXPECTED RESULT

The usual file operation notification should appear while the copy is being performed.

Plasma should not freeze

Another side effect is that you don't know when the operation is really over.

SOFTWARE VERSIONS
(available in About System)
KDE Plasma Version: 5.14.1
KDE Frameworks Version: 5.51.0
Qt Version: 5.11.1

Baloo enabled (for file search not actual content indexing).

ADDITIONAL INFORMATION 

Might be related to https://bugs.kde.org/show_bug.cgi?id=358231