Found in 2.7.0
In the Spaces tab, Loads subtab, if you filter the list (by Story, Thermal Zone, or Space Type) and drag and drop a load definition to a remaining space's definition drop zone, all of the spaces will appear - the filter will be deactivated, although the dropdown menu will still show the previously-selected filter.
Note, filtering by 'Load Type' will not exhibit that behavior, but probably because it doesn't actually hide any of the spaces.
@jmarrec