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Every calibration adds a new profile to the monitor profile list under preferences/displays/color.

I tried to delete the old ones - no success with the usual delete key, nor with option/command + delete.

Do you know how to do it?

Thanks!

Try to delete them the old way, manually. I do this to add calibration profiles I have here and there… I just copy them to my User Home Library --> ColorSync --> Profiles

I guess in order to delete them you just have to go to the aforementioned folder and delete the ones you don't want to be there.

Thanks.

The folder with the profiles is actually in the hard disk library.