SUMMARY
When opening Dolphin (v20.11.70), I get two warnings about a duplicated shortcut. 

STEPS TO REPRODUCE
1. Open Dolphin
2. Observe the warning.
3. Click the "okay" button (twice) to continue to Dolphin and be able to use Dolphin as usual.

OBSERVED RESULT
I receive two warnings. The first one is 
"There are two actions (Show Hidden Files, Donate) that want to use the same shortcut (Ctrl+H). This is most probably a bug. Please report it in bugs.kde.org"
After clicking "OK" the first one is succeeded by the warning 
"There are two actions (Show Hidden Files, Donate) that want to use the same shortcut (Alt+.). This is most probably a bug. Please report it in bugs.kde.org"

After clicking "OK" on both warnings I get to use Dolpin as usual, although View => "Show hidden files" shows CTRL+H having been set as a shortcut to this action, while Alt+. is the normal shortcut.

EXPECTED RESULT
The expected result would be to be met without warnings. :-)

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Neon Unstable Edition
(available in About System)
KDE Plasma Version: 5.19.80
KDE Frameworks Version: 5.74.0
Qt Version: 5.14.2

ADDITIONAL INFORMATION
Nothing much to add. This duplicate shortcut is a bit a nuisance to me personally, but those that usually use the shortcut to show/hide hidden files will find this a greater issue.