Bug 404026

SUMMARY
As part of my normal workflow, I organize many thousands (+10,000) of images (.jpg) in multiple directories. Dolphin seems to be one of the most intelligent file browsers for browsing these directories as it only seems to load what it needs.  However, I have discovered a choke point:

STEPS TO REPRODUCE
1. Open a directory with over 10,000 images
2. Select around 1,000
3. Perform 'Cut' operation
4. Paste in another folder

The above results in enormous delay and freezing of the entire shell.  The dolphin window you paste into does not seem to lag during this process, though.  What's strange is the files seem to be pasted in right away but the rest of the OS including the Dolphin window where the cut operation happened are completely locked up. This can last over 5-10 minutes depending on the amount of files cut and pasted.

The jpg files average in dimension of about 180x180 pixels.

OBSERVED RESULT
Delay of over 5-10 minutes, Plasma shell freezes along with one of the Dolphin windows (where the files were cut from).

EXPECTED RESULT
Nominal delay

SOFTWARE/OS VERSIONS
Windows: 
MacOS: 
Linux/KDE Plasma: Kernel 4.15.0-45-generic
KDE Plasma Version: 5.12.7
KDE Frameworks Version: 5.44.0
Qt Version: 5.9.5

ADDITIONAL INFORMATION
System is a 16 core Ryzen 2700X with 32gb of memory @ 2933MHz.  Given that Dolphin is so snappy in all other places, this just seems like an unusual delay.