Bug 468068

SUMMARY
I wish to set up Night Color Mode in a way that I can turn it off and on manually, but having it Off by default at startup.
But playing with the options, I came accross some confusing behaviors.

There are several options available: 
- Always off:
This one is not really useful, as when I left-click on the icon on the systray, instead of turning on the night mode as I would expect (which would reflect the behavior of every other systray icon and the 'Always On' option), it opens the configuration panel.

- Always on:
When I left-click on the systray icon, it toggles night color mode on and off (as intuitively expected). 
Configuration is accessible with a right click on the icon, consistently with any other systray applet. 

So we can see that "Always Off" option makes the systray icon behaves inconsistently from when "Always On" is set.

PROPOSITIONS
How about merging the "Always off" and "Always On" options into a "Manual" option.
The systray icon will then behave like when "Always on" is set, with the difference that instead of forcing it to 'On' at startup, it remembers its last state manually set by the user.
We can also imagine a set of options for manual mode, that proposes:
o Remember last state
o Starts On (so Night Color Mode is On on startup by default, and left click on icon toggles it off and on)
o Starts Off (so Night Color Mode is Off on startup by default, and left click on icon toggles it on and off )

That would make both the configuration options and the interactions with the applet more intuitive and more consistent with how other applets on the systray behave. 
As a result, it will feel to be more at the service of the user.


STEPS TO REPRODUCE
1. On the System Settings section for Night Color Mode, chose either "Always On" or "Always Off"
2. Interact with the systray icon

OBSERVED RESULT
The icon does not behaves the same way depending on the chosen option, and there is no option that actually lets the user to manually tell the system which mode it wants to start with while allowing for easy toggle on/off.

EXPECTED RESULT
Having the systray icon for Night Color Mode to behaves a bit more like the other icons (left click for toggle on/off, right click for menu and access to settings), and allows the user to tell the system in which mode its should start (on / off / last state) 

SOFTWARE/OS VERSIONS
Linux: Fedora 37
KDE Plasma Version: 5.27.3
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8