I'm picking up again the idea I had in JENKINS-28617 : It would be great to have a Groovy script that can be run before any of the Active Choices parameter Groovy scripts are run.

Most of the time, I read an XML file to construct the data for an HTML form field. But I have to do it every time (seven times for my current form), which results in redundant code and slower performance.

So, my suggestion is that it should be possible to have a Groovy script that's run before all the other Groovy script run. Like for the Active Choices Reactive Reference Parameter, it should be possible to define what Groovy variables can be seen in other Groovy scripts.