SUMMARY
Seeing the vast majority of issues with Plasma Session on Wayland have finally been fixed, I decided to try switching from X11 again after years of waiting. Apart from some annoying but bearable intermittent bugs, there's one persistent issue I'm now encountering with Dolphin:

Holding Control or Shift to copy or move files no longer seems to be working. Upon click-dragging an item, I'm always asked if I want to either copy or move that item. The menu even shows the Control and Shift shortcuts, but it's as if the buttons are no longer detected.

STEPS TO REPRODUCE
Either open two Dolphin sessions or use one with split view. Go to different directories and click-drag files between them while holding the Control or Shift key down.

OBSERVED RESULT
Dolphin acts as if no key is being held. It will ask you whether to copy or move the file instead of automatically doing so based on the key held.

EXPECTED RESULT
On X11 holding Control while dragging the item copies it whereas holding Shift moves it without a prompt.

SOFTWARE/OS VERSIONS
Operating System: Manjaro Linux
KDE Plasma Version: 5.26.4
KDE Frameworks Version: 5.101.0
Qt Version: 5.15.7
Kernel Version: 6.1.0-1-MANJARO (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 3700X 8-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: AMD Radeon RX 570 Series

This is still an issue in KDE 5.27.5 / Dolphin 23.04.1. Is the problem known to the developers and any solution expected? As a workaround I simply got used to pressing and holding control / shift before I click the mouse button to drag the file, which fixes the issue between different tabs in split view but still causes the prompt between different Dolphin windows.