FileDialog.SaveFile mode is unusable

On Linux, because I don't run Gnome, I always get the QML version (which is already a loss in functionality compared to Qt Quick Dialogs 1, even if it worked well: there's no sidebar for frequently-accessed folder shortcuts). And saving a file is impossible.

1) The Open button should be labeled Save
2) After I type a valid filename to save, the Open button is still disabled; but hitting enter gets it to be enabled. I should not need to do that. (If the window loses focus, e.g. if I focus another window, somehow also the Open button will get enabled.)
3) Hitting Enter a second time does nothing: but clearly my intention is to actually save. Why is there no default button?
4) If I then reach for the mouse to counter-intuitively hit the Open button (to actually save), it turns out the selectedFile property is not a URL at all, despite what the docs say: it's just a plain old path.
5) (noticed while taking a screenshot) If I click outside the dialog, it dismisses, even if the main window itself did not have focus. That doesn't quite make sense: it's not an intentional dismissal, it's a stray click.
6) After re-opening, it's now pointing to a different location! Not the location that was declared on the currentFolder property.

I'm trying to fix qtlocation/examples/location/geojson_viewer which actually uses a save dialog. Naturally, since it's expecting a URL, it calls toLocalFile() on it, which... generates an empty string! (For me that's a bug, but a different one. I suspect someone will resist changing this misbehavior, too. So it's very important that when we say we are generating a URL, we actually do: it has to start with file:/// so that toLocalFile() will work.)