An alternative would be to use a couple of “when” statements.
(if the model actually would look like this you would obviously move the when statements up to the container confgA/confgB level)
container confgA {
leaf-list A {
type inet:ipv6-address;
tailf:cli-list-syntax;
when "not(../../confgB/confgB1/B)"
}
}
container confgB {
container confgB1 {
leaf B {
type empty;
when "not(../../../confgA/A)";
}
}
}
If you want to customize the error message of the when statement: