Question: As I am writing my first grails webflow I am asking myself if there is anyy tool or script what can visualize the flow?

Result can be a state diagram or some data to render in a graph tool like graphviz.

Answer: 
There's no tool around currently that will do this for you I'm afraid. I've implemented something myself before, but this was very simple and was not automated in any way. It was a simple template where the model was a step number:

```
<g:render template="flowVisualiser" model="[step: 2]" />

```

You would have to put this in every view of the webflow, changing the number for whatever step it was. The template itself just had a row of images for each of the steps, and there was some gsp logic in the style of each image so that if the model passed in was step 2 (for instance) or above then this particular image would have opacity 1:

```
<li>
    <div class="${step >= 2 ? 'step-completed' : 'step-todo'}">
        <img src="${resource(dir:'images',file:'2.png')}" />
        <h4>Do this step</h4>
    </div>
</li>
...

```

I know it's not fancy and it's a bit of manual labor but it worked just fine for me :)
probably this could be a solution for all people using intellij: <http://www.slideshare.net/gr8conf/gr8conf-2011-grails-webflow>
Slide 25