SUMMARY

The multi monitor arrangement does prevent panels that are set to "windows can cover" from appearing when hovering. 

The issue is clearly, that the second monitor borders to the area, where the panel is located. 

STEPS TO REPRODUCE
1.  Put the second monitor in the display configuration ABOVE the primary one. 
2.  Set a panel bordering that area to "windows can cover" (so a panel at the top, in this example)
3.  See that you cant reliably (if at all) bring that panel back, by hovering over its activation area. 

OBSERVED RESULT

Panel does not reappear, until I remove the second monitor from the bordering area. 

EXPECTED RESULT

The panel reappears when hovering over its designated space. 

Operating System: Garuda Linux 
KDE Plasma Version: 5.27.8
KDE Frameworks Version: 5.110.0
Qt Version: 5.15.11
Kernel Version: 6.5.7-zen2-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 4 × Intel® Core™ i5-6200U CPU @ 2.30GHz
Memory: 7,4 GiB of RAM
Graphics Processor: Mesa Intel® HD Graphics 520
Manufacturer: HP
Product Name: HP EliteBook 820 G3

ADDITIONAL INFORMATION

I tested this in Wayland.

I wanted to see, if this was a Wayland-exclusive bug, and then switched in SDDM to my X11 session. 
Now, inxi -F shows me the following data, which does indicate - together with the 'about this system' KCM - that I am still in Wayland nonetheless. This is most likely a quirk with my distro, as they just recently added this. 

> Display: wayland server: X.org v: 1.21.1.8 with: Xwayland v: 23.2.1 compositor: kwin_wayland

Let us assume, for now, that this is not confirmed in X11. 

PERSONAL NOTE: 

I am running Plasma 5 with Wayland for 2 Weeks now. 7/8 bugs I discovered, are related to "windows can cover" panels.