Usually, you get extra swaps from manually matching 5+ gems or if a manual gem match creates a cascade into a 5+ match.
However, I can’t tell exactly when it is; but, Nissa4 seems to be able to get extra swaps from other means - it appears to be during gem conversions (usually with Eidolon of blossoms involved
I was able to reproduce this issue with Nissa, Worldwaker in Training Grounds today. I was able to get 5 extra swaps in a turn, which is not possible through 5-gem matching alone.
My deck consists of:
Animist’s Awakening
Song of Creation
Cultivate
Omen of the Hunt
Leafkin Avenger
Reclaim the wastes
Skyclave Pick-axe
Turntimber symbiosis
Labyrith of skophos
Nylea, Keen-Eyed
I took a screenshot of the battlelog, though I’m not entirely sure how to get it to you @Oktagon_Support .
The only thing of note is my Leafkin Avenger was disabled during the turn it happened, and several times throughout the loop my Omen of the Hunt got destroyed and triggered, but since I had a full hand I declined to fetch a land from it.