This is a follow-up to https://github.com/jenkinsci/jenkins/pull/2926. In this PR Zdenek Soukup introduced the "enableTopButton" option in /lib/form/repeatable.
The same control could be trivially applied to other repeatable controls in /lib/form. See the referenced pull request for change and test examples.
Merged in https://github.com/jenkinsci/jenkins/pull/2926