Well using javascript and knowing the row ID's I can hide/show/toggle each row... which I guess works. But would be nice if something was a bit more built into the control. If there is one, I can't seem to find it.
Unfortunately there's currently no built-in function available to hide specific rows. It's expected that if rows are added manually for the TIWAdvWebGrid you can also leave out rows that shouldn't be displayed manually. For the TIWDBAdvWebGrid it's expected that filtering rows is performed on dataset level.
However, using JavaScript to hide rows based on the row ID is a good workaround.