I have added a free text field in my tickets and made it mandatory (2).
Values A, B, C, and D are allowed by the drop-down list.

Currently, the ticket defaults to "A" and never prompts the agent to change
the value (all of the types are equally common so there is not truly a
"default") value.

I want to force agents to examine this value before the ticket can be
closed.

How can I achieve this?

I tried adding an additional entry like this at the top:

$Self->{'TicketFreeText1'} = {
'' => '-',

However, OTRS accepted this '-' as a valid default value, which was not my intention.

Thanks in advance for your suggestions,
Hugh