I need to built a custom filter similar to "Incomplete Tasks" that would additionally ask me for a specific user and show me only those of that user.

Problem is: the conditions inside the default "Incomplete Tasks" are two lines separated by a OR clause. Therefore, if I do the same adding a third line to request the username with a AND clause, logical precedence will likely give weird results since I want "(A OR B) AND C" and not "A OR B AND C". Since filter lines does not gives the option of parenthesis, I think I'm screwed.

Ideas?