This feature would be helpful in the case where a User Defined Variable (UDV) is changed.  Currently when a value is changed and the "Insert" button pressed the "Selection" list goes back to the top.  While in small lists this is not a big deal in big lists this is a big deal.  If one looks at the attached screen capture example the slider for the "Selection" list is very small.  The small slider reflects that fact that the list of UDV is large, about 2,200.  It takes about 70 presses of the "Page Down" key just to get to the middle of the "Selection" list.   In the use case where a group of three UDV need to be deleted that are in the middle of the list it would take 210 presses of the "Page Down" key to complete the task.  70 presses for the 1st UDV to be deleted.  Another 70 presses for the 2nd UDV to be deleted (140 presses so far).  Another 70 presses for the 3rd UDV to be deleted (210 presses total).  But if the Filtered Selection List requested feature were implemented the count of "Page Down" keys pressed could go down to zero.  

There are may more uses cases where the Filtered Selection List would be of value.  Another use case example is if the setting for UDV with the string "timeout" all needed to be increase by 20 percent and all the UDV have some other string preceding and following the string "timeout".  Use of a Filtered Selection List would save having to page through all 2,200 UDV to find the UDV that need changed.