I can reproduce this on Neon Testing as well as git-master

This was semi-intentional at the time as there's really not a major advantage to resizing the window — let alone maximizing it. However use cases and people are diverse, so I guess there's probably no *harm* in remembering state here. It's an easy patch. Tracey, would you like to try your hand at it? You can copy what I did in https://invent.kde.org/plasma/drkonqi/-/merge_requests/281 to add this to DrKonqi's windows.

Sure, I can give it a try this week

I believe the reasoning is still valid: everything in Welcome Center appears best at its default size, and growing/shrinking/maximising the window has little benefit. Even moving the window — we want to show it in the center of the screen.

So, I still prefer not to remember anything. If a user does change anything, I wouldn't want it to appear later at an odd size (for example, when showing an update).

(In reply to Oliver Beard from comment #4)
> I believe the reasoning is still valid: everything in Welcome Center appears
> best at its default size, and growing/shrinking/maximising the window has
> little benefit. Even moving the window — we want to show it in the center of
> the screen.
> 
> So, I still prefer not to remember anything. If a user does change anything,
> I wouldn't want it to appear later at an odd size (for example, when showing
> an update).

Are you sure everything appears best at is default size?
Even the "Share Anonymous Usage Information" page where you have to scroll down in windowed mode compared to no scrolling maximized?

As for the user changing anything, like maximizing it, what is the problem with respecting the user's preference on his own computer?
Is the update changelog using exactly the same window as the welcome center?
What if I prefer to maximize the update changelog too and read it like that?
Should I have to do that again on the next update?

I for example hate the fact that Plasma doesn't have a general option in the System settings to set the "Open maximized" preference once and for all for all new windows that have not been opened before to have something to remember.
So I have to "teach" every every single window that I prefer it to be maximized if I open it next time.
If I have "taught" the Welcome Center that I prefer it maximized, if I open it again, I would have no problem that the Update changelog window will also open as maximized as that's my general preference.
Plus having windows maximized helps me focus only on that content of that window, and not distract me with the windows that I might have stacked behind, some maybe with something flashing, or videos playing like a web browser, video players, audio players with music visualizations, etc. 
Maybe in the future I will also set some nice video wallpaper so that would also be distracting if I have something to read in a window.
In my opinion, as long as Plasma doesn't have a way to set a general opening size preference, it's ok to open windows as windowed, in the center of the screen, but if the use has maximized it once, that should be remembered for the next time it open the same thing.

(In reply to John from comment #5)
> I for example hate the fact that Plasma doesn't have a general option in the
> System settings to set the "Open maximized" preference once and for all for
> all new windows that have not been opened before to have something to
> remember.
Quick correction: this does exist in System Settings > Window Management > Advanced > Window Placement: Maximized

A possibly relevant merge request was started @ https://invent.kde.org/plasma/plasma-welcome/-/merge_requests/192

(In reply to Nate Graham from comment #6)
> (In reply to John from comment #5)
> Quick correction: this does exist in System Settings > Window Management >
> Advanced > Window Placement: Maximized

Wow, this is what I love about Plasma and KDE software in general...
You sometimes want so much a feature and even ask for it and them someone tells you that it's already there, this is really awesome!
Sorry for not digging enough trough the control panel to find it myself.
I will try it next time I will do a clean install of the OS to see if I like it as not a lot of windows have already been "taught" about my preference and I will not notice much.
If I don't like it by default, I would still be very happy to teach every window one by one, considering the fact that they can remember what I prefer for each case.

Thank you very much for both the fix and for the mentioning of this configuration option!

Git commit 528c2f8d2e9bef15a20b69d869264e6e4e0e5e26 by Oliver Beard, on behalf of Tracey Clark.
Committed on 14/02/2025 at 20:47.
Pushed by olib into branch 'master'.

Remember window geometry

Remember window size and maximization. On X11 also remember position.
This makes the behavior consistent with similar work that was done
for the Konqui window.
FIXED-IN: 6.3.1

M  +1    -0    .gitignore
M  +5    -0    src/qml/Main.qml

https://invent.kde.org/plasma/plasma-welcome/-/commit/528c2f8d2e9bef15a20b69d869264e6e4e0e5e26

Git commit 60bebde282be6c1132bec157aec4e9e1f1e33d8d by Oliver Beard, on behalf of Tracey Clark.
Committed on 14/02/2025 at 20:55.
Pushed by olib into branch 'Plasma/6.3'.

Remember window geometry

Remember window size and maximization. On X11 also remember position.
This makes the behavior consistent with similar work that was done
for the Konqui window.
FIXED-IN: 6.3.1

M  +1    -0    .gitignore
M  +5    -0    src/qml/Main.qml

https://invent.kde.org/plasma/plasma-welcome/-/commit/60bebde282be6c1132bec157aec4e9e1f1e33d8d