I did Search with Scan and it appears you have to manually scroll through a limited Custom selection.
I use the same technique on one of my scanners to find any new frequencies in use while I scan the normal systems. It should automaticly search all the search ranges you have enabled. Check that each of the 10 search ranges, or how many you choose to use, are actually enabled.
Check in Sentinels profile in the Custom Search tab to set ranges and other settings as well as the bank Status. I let the scanner record everything unattended and have set the dealy to -10sec to make it continue scan after 10 sec or it will stop the search at any interference or longwinded converstion or carrier.
I tend to use smaller frequency segments to not have to scan any cellular or pager frequency bands or similar that would need me to avoid a lot of frequencies. The number of avoids are maxed out at 255 and if I remember correctly there's no notification that you go above that number. It just pushes out the oldest avoid from the list that will enable that frequency again.
The scanner has a discovery function that lets you tick a box to only log new hits that do not exist in the database or in any loaded favorite list, but that function already broke in a firmware version for BCD436/536 and to my knowledge haven't been fixed and have been inherited by the SDS scanners.
/Ubbe