Custom Select fields can be added by clicking on the big + button in the Fields manager, on both Organization and Event levels, and selecting the option Select in the dropdown offered.
Planners can edit the name of the field (e.g. Accommodation), label for the field visible to contacts and participants (e.g. Accommodation need) and the category the field belongs to (e.g. Personal information).
In order for this field to work, planners need to add possible values in the Validation section that will represent options offered for this field (e.g. Yes, No, Maybe, etc). Only one option will be available for selection.