Nested List Checkbox for React

Yes. When some but not all children are checked, the parent is indeterminate rather than checked or empty, so people see a partial selection without counting. The parent gets checked when all children are on and indeterminate when some are.

Every child takes the parent's new value: checking it selects all, clearing it clears all. Clicking an indeterminate parent checks it, which completes the partial selection. The parent's change handler sets the three children, and the parent follows from them.

Yes, but not by setting it. The parent's state is derived from the children each render: all checked, none, or some. Ticking a child changes the children, and the parent updates with them.

You can repeat the pattern, with each parent derived from its own children, but past two or three levels it gets hard to follow. For deep hierarchies, use a Tree View with checkboxes and collapsible branches, or flatten the list into headed groups.

Indent each level: the children here are a FieldGroup with ms-6, a logical margin that flips in right-to-left pages. A heavier parent label helps, and border-s ps-4 on the child group adds a guide line.

Every checkbox has its own label, Tab moves from the parent through the children, and Space toggles. Screen readers announce the indeterminate parent as mixed or partially checked. The indent is only visual, so a parent label that says what it controls (Select all features) carries the relationship.