I am unable to edit the list of selections in the Options box for most of the Ticket Custom Fields (Single Selection, Multiple Choice, Popup Menu). The Options box is greyed out and there is a Clear button on top of it. For a few of the Custom Fields I am able to edit the value in the Options box and there are also Browse/Upload buttons available.
Why am I able to edit some of the lists but not others? What does the Clear button do if I click it?