Outside the UN headquarters in Geneva, the flags of the member states are flown in the 'Allée des Drapeaux'. However, looking at photos of the flags, they never appear to be flown in the same order.
Consider the following two photos; according to Google Streetview the left was captured in 2017, while the right was captured in 2019. The flags shown at the front in both images separated from the others appear to be those of Vatican City & Palestine, which makes sense as they are observer members of the body rather than full members. Behind them, however, appear to be the flags of Belize and Benin in the left-hand image, and the flags of Gambia and Georgia in the right-hand image.
I presume it's something to do with alphabetical order, as the UN FAQ states:
Q: How are the flags raised outside the UN Headquarters in New York?
A: The flags are raised manually by UN Security officers every weekday morning at approximately 8am and lowered every weekday at around 4pm, except in the cases of bad weather. The flags are organized in English alphabetical order from north to south. On weekends, only the UN flag is raised.
What are the rules for the arrangement of the flags in Geneva?