Adding EXIF line

I am looking for software with GUI that can add an EXIF line to QT file. Alternatively, a software with GUI that can copy entire EXIF data set to another QT file and replace the old EXIF. I am aware of EXIFTOOL and its GUIs, but was not able to perform the above tasks.

(Tested answers only, please)

Do you mean the metadata (keywords, description...) of video files?
If yes you can use Adobe Bridge to copy & paste IPTC data to a bunch of different video formats.

Can I add this line using Adobe Bridge:
CompressorName: H.264
?