Ability to use all elements only once

[adamberecz]

Then they should disappear from the element list

[cbaxter7]

Could it be introduced that specific elements are only used once also?

[adamberecz]

This would require disabling cloning functionality, which is possible, so I've extended the example related to Discussion #66:
https://stackblitz.com/edit/github-bmamqp-72epfq?file=src%2FApp.vue

Generally if you define schema.builder.clone = false for an element new copies of it will become "unclonable".