The "Other IDs" field records the "ID" of the problem in other work reporting/tracking systems, or in related information sources. A common example is a reference to IST's RT system, e.g. of the form
[UW-RT #69899]And there are other references that can appear in this field.
The intent is that, where relevant, it be the text one ought to include in a Subject line when communicating via email with other work tracking systems.
They can also appear in the Dependencies and See Also fields. That wasn't always the case, and not being able to do so was the primary reason for this field to exist. So this field isn't really necessary any more.
Since the IDs can contain blanks, the values are comma separated in the Other IDs field.
When specifying this field in a customized sort or display, use the name "id_other".