When using the DAM filter to save smart collection, the click action on the panel to save smart collection does not maintain focus and the click action is actually handled by the filter, which will result in a filter search update
No smart collection can be saved if the panel is above a checkbox, as the filter will be selected and applied
This is a bug that is fixed in 6.5.
A request for inclusion in 6.4.5 has also been opened under the internal references CQ-4240323 / NPR-29000
A support fix is also available for version 6.4.3 (see below)