When string-based attributes (String, List, Set) are shown as Displayed Attributes, once discrete values are added to the attribute these are all shown via a pop-up list via the triangular icon at the right end of the attribute value edit box. For fast entry, autocompletion using matched list items is also possible. However, do bear in mind limitations on the length of and number of entries in these lists.
Suggested Values
If the list of likely values is known in full (or part) before the main data is added to the document, it is easy to pre-populate the attributes value list via the 'Suggested' box on the relevant Inspector for User and (some) System attributes.
Enter the list of values as a semi-colon delimited list without any enclosing quotes. To pre-populate an attribute with values 'Ant', 'Bee' and 'Cow' the unquoted string to enter into the Inspector's suggested box is Ant;Bee;Cow. A terminating semi-colon may be used but is not required. It can be helpful to prepare the list in another note if it is long and will extend beyond the visible portion of the suggested box.
If adding a list to a document that already has values, it may be useful to first test the new list in a new document to ensure the correct values show up in a Displayed Attributes pop-up. Indeed, this method does not prevent new values (not in the suggested list) being used. If trying to assert a fixed list of values and new values are seen in the pop-up list, note the new value(s) and use an agent to find and correct the notes with the unwanted values.
Values that appear only in the suggested list, i.e. are not (yet) used by an actual note, are not included when using the values() action.
This method replaces an older approach of making 'seed' notes as placeholders for desired prepared values.