The "Watchlist" shortcut shows a filtered ticket list that only contains tickets that have been marked with the "flag" in the ticket list by the current user. The purpose of the watchlist is that a user can track individually marked tickets at any time without being responsible for them him-/herself. View: "My Watchlist".
Adding a ticket to the personal watchlist is done directly in the ticket list by clicking on the flag icon (first column of the ticket list). Alternatively, the "Set flag" function can be used by right-clicking on a list entry. The ticket is on the watchlist when the flag is filled in.
A user can only mark tickets for him-/herself personally.
Via the default view "My watchlist" or the default filter "Watchlist", the personal watchlist can be accessed in every ticket list.