The pipline DSL documentation explaines that an multiple choice dialog can be used with the input command. The documentation however is not very detailed. I had to read the code of the extendedchoiceparaemter to circumvent some problems (e.g. when the muliSelectDimiter parameter is missing the plugin throws a null pointer exception. )

Im, however, stuck now with an interface problem it seems. Please see attached console output. Assumption:  It is tried to invoke a method of the plugin which doesnt have the expected signature anymore.

stage('file input') {
    node {
        
        script {
        def userInput = input  message: 'Let\'s promote?', ok: 'Release!',
 parameters:  [$class: 'com.moded.extendedchoiceparameter.ExtendedChoiceParameterDefinition',name:"test",  multiSelectDelimiter: ",",
 type: 'PT_MULTI_SELECT',value: "first,second,third"]
echo "userInput"
}
    
}