While in the backlog view, if you attempt to filter by Portfolio Item, you can type 3 letters or a keyword to find a Portfolio Item to filter by and then select it from the filtered list. Although the UI allows you to select multiple Portfolio Items with this filter, if you have several that contain the desired keyword, you have to repeatedly search and select each one. It would be helpful to have the filter have a "Contains" operator in addition to "is" so that if the keyword is on multiple Portfolio Items, you do not have to keep searching for a Portfolio Item name by the keyword to grab each one that applies.