This guide will contain the locations of twinkle slimes as updates day-by-day.
Twinkle Slime Locations in Wiggly Wonderland Event 2019
The first twinkle slime is located in the quarry.
In the Moss Blanket, see screenshot below. It is near the one way teleporter that gets you back to your ranch.
Just beside ancient door
In the Dry Reef. By the Hobson Letter Talking about his old tree on the main path of the Dry Reef and just behind the Tabby Gordo/Dry Reef Teleporter. Almost impossible to miss.
In Indigo Quary
In the Ancient Ruins.
In the Moss Blanket.
In Indigo Quarry (You'll want to look for a teleporter to get to this island).
In the Dry Reef:
In the Ancient Ruins:
In the Glass Desert near the middle of the map, next to the stairs leading to the Tangle Gordo (or teleporter, if you've already popped the Gordo).
Instantly in sight when dropping down the Entrance to the Moss Blanket:
Going counter-clockwise of the ring of Chimes surroung the Pool. The back side plays Beethoven's Fur Elise (starts where the crosshair is in the pic above).
Just a bit outside your Ranch, before you can even see the Pink Gordo Island.