SUMMARY
When pasting an image from the clipboard into Dolphin, it pops up a dialog with a text box for typing in a filename and a drop down selection to choose a file type.

The defaults for this dialog are quite bad: the file name box is empty - without even a hint and no suggestion of a file extension; and the drop down menu is labeled "Data format" and the default value says "application/x-kde-onlyReplaceEmpty" (which I have no idea what it means and if I choose that it creates a 1 byte sized file).

The drop down already shows useful names for at least some of the mime-types that are offered in the clipboard content (Saying "PNG Image (image/png)" for example, compared to "image/epsi" for some other arbitrary content-type that few people know what it means).

STEPS TO REPRODUCE
1. Use Spectactle to take a screenshot and copy it directly to the clipboard instead of saving as a file.
2. Open Dolphin and navigate to some directory.
3. Hit CTRL+V

OBSERVED RESULT
A pop up dialog comes up, which is a bit confusing, and if typing some name and pressing ENTER, a useless file is created.

EXPECTED RESULT
A pop up dialog should come up with a suggested file name (for example: "Pasted content.png") and the format pull down should default to a useful selection (for example: PNG).

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 5.27.80
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8

ADDITIONAL INFORMATION
I think it will also be useful if the format drop down will sort the suggestions so that the types whose meaning is recognized (i.e. showing a human readable name) are all sorted above all the alternative content-types that are not recognized. Also, when the user selects a different format, the file extension in the file name text box should change to match the selected format.