Often configuration of the plugin or core functionality is missing a feature or option. Many of such 'improvements' just requires modification of jelly script.

It would be nice to have possibility to define custom jelly script which replaces the original one (from the core or plugin) - to be defined on the main/workspace/job/view level.

How it could work?
For example on the 'view' which uses plugin A and B let's define custom jelly script:
original: A/scriptXXXX.jelly (notation 'plugin_name[/directories]/file)
custom: content or file

original: B/scriptYYYY.jelly
custom: content or file

And when jelly engine runs it first looks on the 'custom jelly' definition and later on on the original jell files (for example in stapler:include tag).

This will allow quick and easy customization of any UI element in Jenkins.