Marmalade blockers, like licorice Xs, occupy a space where there is a candy. The marmalade blocker will prevent you from moving the candy encased in the marmalade.
Marmalade blockers aren’t introduced until level 186 but after that, you’ll find them to be a very abundant in the 200s and 300s.
Marmalade blockers are also unique because a majority of the time they are on the board, they’re covering a special candy. Starting in late 100 levels, special candies are given as a default on certain boards. When this happens, you will find a marmalade blocker blocking the special candy–this can special candies like a coconut wheel, a color bomb, a jelly fish.
Marmalade blockers can be cleared either by making a match adjacent to the marmalade or by making a match with the candy contained within the marmalade.
Luckily, marmalade is only one layer so it will only need to be cleared one time.