hugo/docs/content/en/functions/collections/SymDiff.md

title	description	categories	keywords	action	aliases
collections.SymDiff	Returns the symmetric difference of two collections.			aliases related returnType signatures symdiff functions/collections/Complement functions/collections/Intersect functions/collections/SymDiff functions/collections/Union any COLLECTION | collections.SymDiff COLLECTION	/functions/symdiff

Example:

{{ slice 1 2 3 | symdiff (slice 3 4) }} → [1 2 4]

Also see https://en.wikipedia.org/wiki/Symmetric_difference.