You are correct that SID transitions are not available when selecting a SID.
There have been issues with SIDs and STARs having multiple transitions. It looks like there has been some changes made. When I specify runway 20R and ANAHM1 SID, the dropdown box shows “ANAHM1 (ALL)”. I assume all the transitions are available. I think to specify the transition, the transition waypoint should be entered or inserted. The SID chart would be needed to select the transition waypoint.
I haven’t seen anything in Release Notes or fixes for this so I’m thinking this was an undocumented change or fix in one of the recent updates.