Freeze "Select All" at top of list so that it remains visible on longer lists

"Select All" is probably the most used function on any slicer. I am using the November 2018 version at my organisation and the "Select All" option disappears as soon as you start scrolling on longer lists. If one item has been selected and it is a long way down the list, when the user selects the drop down arrow, the list immediately goes to that item. Then if the user wants to revert to "Select All", they then have to scroll back to the top of the list to "Select All". If the "Select All" option was still visible, the user would then not have to scroll. This suggestion is to freeze the "Select All" at the top of the scrolling list.