Welcome! This forum has a treasure trove of great info – Scouters helping Scouters! Just a heads up, though - all content, information, and opinions shared on this forum are those of the author, not the BSA.
I have a registered adult who has been a den leader for the last two years. She is moving from that role to an assistant den leader. I ended her role with the current den and added a new den leader. When I went to the leader roster in Scoutbook, she is no longer listed. Scoutbook returns no record when I search for her name to add her to the roster. She is a registered den leader on our roster that appears on my.scouting.org. Please help.
Just a procedure change will keep this from happening -
Before ending the last position a leader has, add the new position.
In your example, add the ADL position before deleting the Den Leader position.
Because SB does not yet enforce the BSA restriction of one person / one position / unit, a person can be both DL and ADL of the same den in SB, or any other combination of positions.
However, your My.Scouting roster is a different story. This is the official roster. The COR (and delegate) can make changes to registrations for folks in the unit, moving them from position to position as needed. Functional roles can be changed by any of the unit Key 3 (and delegates). Changes in your My.S roster will sync to SB overnight, but den assignments don’t. Unit leadership must assign those in SB after the leader shows up. If the leader is already changed in SB, it just syncs.
Any tweak to a leader’s record in My.S, like an address change, will cause a sync to SB. If the leader’s SB position doesn’t match the My.S registered position, the system will add the My.S position to the adult. To avoid confusion, I recommend changing the official roster to match what the leaders are doing in SB.