After restarting the system (proper shutdown or reboot), dolphin starts into a split window showing the home folder in each part, while it is set to start where it was left, i.e. remember open tabs and folders. I usually have up to ten tabs open in split window mode, in order to move files around, search for particular files etc. After restart, I have to open again those tabs and folders in order to provide a useful environment, which is annoying.
BTW, I believe the German description of the setting is wrong, or it is meant as it is written, but then utterly useless (because the alternative option means basically the same). In German, it says: "Ordner, Unterfenster und Fensterzustand vom letzten Start", which means "folders, subwindows and window status from last start". In other words: Dolphin starts as it has started the last time. And in that it behaves correctly, because last time and the times before (after it forgot the open tabs and folders) it always started the same way as it started before. I can only assume that is not what is intended with that setting (which I have kept for ages), but that it should remember where it last ended. In German, it would be correct to say "letzten Zustand wiederherstellen" or similar, in English it would probably be somthing like "restore last status".
Since there is no other option available to do that, I assume that this is what is meant with that setting.

I know that this is a duplicate of the bug https://bugs.kde.org/show_bug.cgi?id=469656, but that has been closed and related to a previous version.


STEPS TO REPRODUCE
1. open Dolphin
2. open new tabs, open different folders
3. set dolphin to start into the previous state (i.e. the first choice in the settings window "show at start"
4. shut down the system and start it again
5. start Dolphin

OBSERVED RESULT
Dolphin opens only one window with the home folder in it. In my case, it's a split window, I do not know if that is generally the cause, else I would say it starts into the default setting, ignoring previous tabs and folders

EXPECTED RESULT
Dolphin should open the tabs and folders which were open when it was shut down

SOFTWARE/OS VERSIONS
Operating System: Manjaro Linux 
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.13.0
Qt Version: 6.9.0
Kernel Version: 6.12.25-1-MANJARO (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 2600 Six-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: AMD Radeon RX 570 Series
Manufacturer: Micro-Star International Co., Ltd.
Product Name: MS-7B79
System Version: 1.0

ADDITIONAL INFORMATION
It would be nice to have something like a profile manager, which saves all these settings in case Dolphin forgets to restart into the previous state. But I believe that this proposal was already rejected earlier.