Function validate_add_to_variable_list

pub fn validate_add_to_variable_list(
    _key: &Token,
    _block: &Block,
    _data: &Everything,
    sc: &mut ScopeContext,
    vd: Validator<'_>,
    _tooltipped: Tooltipped,
)

A specific validator for the three add_to_variable_list effects (global, local, and default).