This is checked by default in Configure > User Settings, under the Appointments heading, so by default the Departure Task List includes a 1st Available appointment indicator:

However, this functionality is resource-intensive, so if your system struggles to cope, you may opt to un-check this box.

When un-checked , the First available appointment indicator is replaced with a simple appointment search in the Departure Task List:

NOTE: Users with appropriate permissions can achieve the same result by enabling the Configure > Settings > patret.disable first available hyperlink option:

Summary:

If your system is performing well you need do nothing.

If your system is struggling with performance, and you opt to disable this function, de-select the Show the first available appointment time checkbox in Configure > User Settings, under the Appointments heading. You will need to do this on a per User basis.