Shuffle a ragged array
Jelly, 3 bytes in Jelly's codepage

FẊṁ


Explanation:

FẊṁ
F    flatten list
 Ẋ   shuffle the output from the previous line
  ṁ  unflatten the list, shaping it like…


Because the program is incomplete (ṁ doesn't have a second argument stated), the default is to use the program input; thus ṁ causes the output to have the same sublist pattern as the input.

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