The obs tag supports entry of more than one value via a "selectMulti" attribute.
When you enter some text and select a new item from the drop-down, the item then appears within the fill-in field, colored green; however, this item will not be submitted unless the enterer clicks on the Add button. This seems like it may be confusing to users
Once this ticket is completed, if
HTML-577 is also completed, then documentation of this feature should be added to the htmlformentry reference documentation on the OpenMRS wiki.