SUMMARY
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Running openSUSE Tumbleweed, latest updates, KDE Plasma desktop. Using both Dolphin and Krusader as file managers, both in split-window mode (old Norton Commander habit...). My issue is which of the two Dolphin windows has the focus when Dolphin starts; there is no issue with Krusader.

I want the focus to be on the l.h.s. window [column] when I start Dolphin. Thus, in Dolphin Preferences, I set "Start" -> "Show at start" -> "Folders, sub-windows, window status as of last start" (translated from German).

However, annoyingly, Dolphin always comes up with the focus on the r.h.s. window [column]. It doesn't help to exit Dolphin after setting focus to the l.h.s., and there is no setting in Preferences I can chose to help either.
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STEPS TO REPRODUCE
1. Set Dolphin Preferences to display the menu bar and to be in split-window mode at its start, and try several settings regarding folder / window status restore at start
2. Set focus onto l.h.s. window [column], then exit from Dolphin
3. Start Dolphin again

OBSERVED RESULT
Dolphin always comes up with focus on the r.h.s. window [column]

EXPECTED RESULT
Dolphin should come up with focus on the l.h.s. window [column], when the l.h.s. window had the focus at exit from Dolphin

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSUSE Tumbleweed, latest version 20220904
(available in About System)
KDE Plasma Version: 5.25.4
KDE Frameworks Version: 5.97.0
Qt Version: 5.15.5

ADDITIONAL INFORMATION
The issue exists since long, i.e. many versions of KDE Plasma & Frameworks along the Tumbleweed rolling release path. No, I haven't checked other Linux distros with KDE (yet).