Hi @pierre a thanks for posting in the community! If you would like to start with a template I recommend exploring the Lucidchart diagram templates gallery to look through the collections of templates to help you get started.

You can also access templates by clicking the 'Templates' button found in the left menu of your Documents list. From there you should be able to search using keywords to find a template that may help with creating something for your use-case!

For more information I recommend taking a look at our Work with Templates article from the Help Center. 

I hope this helps. Please feel free to let us know if you have any questions!