What you can do is use the dir step, if the directory doesn't exist, then the dir step will create the folders needed once you write a file or similar:

node {
    sh 'ls -l'
    dir ('foo') {
        writeFile file:'dummy', text:''
    }
    sh 'ls -l'
}

The sh steps is just there to show that the folder is created. The downside is that you will have a dummy file in the folder (the dummy write is not necessary if you're going to write other files). If I run this I get the following output:

Started by user jon
[Pipeline] node
Running on master in /var/lib/jenkins/workspace/pl
[Pipeline] {
[Pipeline] sh
[pl] Running shell script
+ ls -l
total 0
[Pipeline] dir
Running in /var/lib/jenkins/workspace/pl/foo
[Pipeline] {
[Pipeline] writeFile
[Pipeline] }
[Pipeline] // dir
[Pipeline] sh
[pl] Running shell script
+ ls -l
total 4
drwxr-xr-x 2 jenkins jenkins 4096 Mar  7 22:06 foo
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
Finished: SUCCESS

There are lots of ways to do this. Here are two ways I can think of off the top of my head:

steps {
  println(WORKSPACE)
}

or

steps {
  def foo = sh(script: 'pwd', returnStdout: true)
  println(foo)
}

Not exactly. There's the deleteDir step, which deletes the current directory, so you could do:

dir('/tmp/jobDir') {
    // your steps here
    deleteDir()
}

If this comes up often enough, you could also just make your own function:

def tempDir(path, closure) {
    dir(path) {
        closure()
        deleteDir()
    }
}

And use it like this:

tempDir('/tmp/jobDir') {
    // your steps here
}

Edit: If you only want to delete the directory if it was newly created, you can use fileExists:

def tempDir(path, closure) {
    def dirExisted = fileExists(path)
    dir(path) {
        closure()
        if(!dirExisted) {
            deleteDir()
        }
    }
}