How to select Multi select checkbox tree

What I was trying to do is there are checkboxes that when they are checked, the sub options will just appear.

I'm not sure how to do this. What I did was put choices 1-6 into a stack thinking that when the sub-option appears the other choices will automatically move/adjust at preview but instead when I select the checkbox, the suboptions will appear but it overlaps the main options below. See picture below

Is this possible to do this?

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