However, there is one argument that could be made that this isn't clearly an official position. You have no other identity.' This is an assigned by someone with some local authority. When Picard is a prisoner, a Cardassian Interrogator/Torturer tells Picard to expect to be referred to 'only as human. This is different than when many characters call Worf by a reference of 'Klingon'. No, the word 'human' is not just Picard's species.'Human' ( Memory Alpha: Chain of Command, Part 2).Picard's role as captain was replaced with this role as undercover operative (assigned by the Federation), until that was effectively replaced by the Cardassians who assigned him a new role. Since Picard is no longer Captain of the Enterprise, he is clearly being officially assigned a different position. Vice Admiral Nechayev who then assigns Jellico as Captain of the Enterprise (so Picard is, quite clearly, no longer in the same position of being active Captain of the Enterprise).Undercover operative ( Memory Alpha: Chain of Command).(It led to Picard being in room, having a rather private conversation with the Klingon Chancellor.) This seems to be a very official position in the Klingon judicial system.Picard fills in after Commander Kurn is attacked.Worf's Cha'DIch ( Memory Alpha: TnG: Sins of the Father).Arbiter of (Klingon) Succession ( Memory Alpha: TnG: Reunion).Assigned by Rear Admiral Noral Satie, Starfleet command, Stardate 41148).(surprise! Picard's been a captain of a starship!).However, I will give this a start to mention some of the more unique assignments. I would think someone more qualified than me could make a good argument for Picard. This answer contains spoilers for multiple episodes. Klingon governor of Haatoria (future timeline in 'All Good Things', if you think that timeline actually 'happened' in some sense).Federation Ambassador to the Klingon Empire (as of the end of DS9).Klingon High Chancellor (for about 5 seconds during the DS9 finale).First officer of the IKS Rotarran (Dominion War).Commander of the Defiant (intermittently throughout DS9 and in First Contact).Strategic operations officer on Deep Space 9 (most of DS9).First officer on the 1701-D (altered timeline in 'Parallels').Ops officer on the 1701-D (during 'The Most Toys' when everyone thinks Data is dead).

Tactical officer on the IKS Hegh'ta ('Redemption II').Security chief on the 1701-D (remainder of TNG).Bridge officer on the 1701-D (season 1 of TNG).I can find at least 10 or 11 positions for him that fit your requirement: He appears in more episodes than anyone else, over two different series, and also has a tendency to briefly take on positions in the Klingon Empire during episodes that focus on it.

Memory alpha measure of a man