STEPS TO REPRODUCE
1. Open Dolphin
2. Make sure at least two tabs are open
3. Press F10 to create a new folder, doesn't matter name, OK (this will also work on an existing file or folder, you just need to make sure there's something in there that you can highlight and rename)
4. Press F2 to rename - don't type anything or press return
5. Press F10 again to create another new folder, doesn't matter name, press OK or Cancel (doesn't matter which, but has to be one of them).

OBSERVED RESULT
Cursor keys up and down do nothing. A single press or left or right cursor key will cause the tab to the left or right of the current tab to be switched to.

EXPECTED RESULT
Cursor keys up, down, left or right highlight different objects in the current folder/tab.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20221227
KDE Plasma Version: 5.26.4
KDE Frameworks Version: 5.101.0
Qt Version: 5.15.7
Kernel Version: 6.1.0-1-default (64-bit)
Graphics Platform: X11
Processors: 4 × Intel® Core™ i5-7200U CPU @ 2.50GHz
Memory: 15.5 GiB of RAM
Graphics Processor: Mesa Intel® HD Graphics 620
Manufacturer: HP
Product Name: HP ProBook 450 G4

ADDITIONAL INFORMATION
I notice that the state you get in after following the steps to reproduce is the same state that you get in if you press the tab key enough times (two) to get the cursor into the tab bar.