First I fixed the ActionItem label width exiting the button boundaries mentioned in BUG: 385794
https://bugs.kde.org/show_bug.cgi?id=385794
Example of the bug:
Since We cutoff the ActionItem text, I then changed the minimum width to 300px since it fits the *english* text naturally.
I could probably change that to preferredWidth=300px (with minimumWidth=200px) if you want a desktop widget to start at 200px width, but a "panel widget" open as 300px. A systemtray widget is always ~400x330px.
I also multiplied the minimum widget size so it scales with the DPI.
You can test with:
QT_DEVICE_PIXEL_RATIO=2 plasmoidviewer -a package
Lastly, I added my commented out mockup of the vaultsModel since plasmoidviewer doesn't expose vault's plasmoid.nativeInterface. If you won't use this then I'll remove it.