The actual longest word according to the Swedish academic word list is “Realisationsvinstbeskattning” (Capital gain taxation)

But as with many languages we can add together several words in some ways so according to Guinness world records (yeah, they suck) it’s “nord-väster-sjö-kust-artilleri-flyg-spanings-simulator-anläggnings-materiel-underhålls-uppföljnings-system-diskussions-inläggs-förberedelse-arbeten.” (North western lake coast artillery flight reconnaissance simulator construction material maintenance follow-up system discussion posts preparation work.)