This problem note describes a situation in EG 4.1 where you use an outer join containing a filter (i.e. the predicate is in the ON clause rather than the WHERE clause). But how do you actually tell Enterprise Guide's query builder to include a filter in a join? The problem note says this is fixed in 4.2 so did they change the user interface, or is there already an option to do this in 4.1, and the option isn't working?
Yes, the user interface is changed. In SAS EG 4.3 (and probably also in EG 4.2) the Join Properties window was added a possibility to enter "Filter to include in the 'join tables on' clause". What you enter here, won't appear in WHERE clause but will be added to the ON clause. E.g. "your_additional_filters" in following code:
...
FROM table1 t1 LEFT JOIN table2 t2 ON (t1.key = t2.key AND (your_additional_filters) )
WHERE some other conditions