Anno 1800
How often can Alonso Graves, Aarhant and The Editor be used in a turn?
The rulebook's effect objective cards section limits these three to one use per turn each.
Once per turn each, so you can use all three in one turn. Other population cards that grant extra actions are not covered by that limit. Beryl O'Mara is the exception and can be used again by paying two exploration tokens each time.