I have installed the postbuildscript plugin on Jenkins. I can see it is installed but the plugin is not visibly there. As in, the screenshot you see in the plugin's page https://plugins.jenkins.io/postbuildscript/ is not visible in my jobs. There is no postbuildscript section when configuring my jobs.
I've tried manually adding the postbuildscript section to my pipeline scripts, but this does not work as Jenkins does not recognise the function name.

I saw a similar ticket https://issues.jenkins.io/browse/JENKINS-34656 and tried to use the chrome devtools, but I didn't find anything with this.