I added user context tags(name and task attributes) in my code, and I can see the user context data on the events when I look them up in the UI.
However, trying to filter by those attributes(i.e. user.name:"myusername" or user.task:"mytask") fails to bring up any results.
Thanks!
According to technical support, the correct syntax to filter by user attributes is user:username:ausername(the documentation is currently erroneous in indicating a dotted syntax of user.username:aname).
Also, apparently, only user attributes defined in the documentation are indexed, and not custom attributes. Those have to be normal tags to be indexed.