Perhaps you can describe your request in more detail.

Sure. The copy artifact plugin creates a special type of build parameter called build selector. If you use that parameter for the build, you get a combo box when starting the build that is populated
with the possible build numbers to copy artifact from.
This is great, but when you trigger a parameterized build from a different project you can't pass values to that type of parameter (the build selector).
This is a problem since the build selector is very convenient when triggering jobs manually but I need a way to pass it when I trigger a build a different project also

Agreed this is a necessary feature. Having a solution so that I can trigger builds via a job, and then in the situation of "rebuilding" a failed child job, I'd like to then be able to select the build that the child job should reference for copying artifacts.

This looks like a text parameter when you print it from a command line or view it in a parameter analysis plugin (Simple Parameterized Builds Report, "Rebuild Last", etc.); you might be able to pass something like this as a workaround:

<TriggeredBuildSelector plugin="copyartifact@1.38">  <fallbackToLastSuccessful>true</fallbackToLastSuccessful>  <upstreamFilterStrategy>UseNewest</upstreamFilterStrategy>  <allowUpstreamDependencies>true</allowUpstreamDependencies></TriggeredBuildSelector>