If I edit an image whose filename contains accented letters, and I choose "Save As", non-ascii bytes are converted to %XX (hex representation) in the filename offered. E.g. I edit "béla.png", choose Save As, the offered new name is "b%C3%A9la.png". If I do not edit this name, the image is stored with this name (with percent sign and hex digits in the filename, i.e. this string is not converted back to a normal accented letter).

The "Save As" dialog should show the filename in a human readable form, it should be the same as the filename used so far, accented characters should be treated exactly as nonaccented ones are treated.

(I have a fully UTF-8 environment, locales set correctly, filenames all encoded in UTF-8. I work with local files.)