One of the functions that didn’t make the initial migration cut in the MarcEditor was the ability to edit the 006/008 in a graphical interface. I’ve added this back into the OSX version. You can find it in the Edit Menu:
Invoking the tool works a little differently than the windows/linux version. Just put your cursor into the field that you want to edit, and the select Edit. MarcEdit will then read your record data and generate an edit form based on the material format selected (or the material format from the record if editing).
Questions — let me know.