I have my spectacle configured to open "save a rectangle" or whatever it's called. It lets me select the part of the screen that I want, then I double click in the area and I have it copied to my clipboard, and from memory there is a setting somewhere that automatically saves it to ~/Pictures/Screenshots
I now use flameshot, which has a similar auto save when copying feature
Are you closing the spectacle window after taking a screenshot? I found that you need to keep it open for the image to stay in the clipboard. When I have the time I can check how I've set it up if that doesn't work for you. Although I only copy to clipboard, not save as well.
KDE
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Plasma 6 Bugs
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