I want the user to have the possibility to withdraw from his Work task. How do I do that?

If you want the user to easily withdraw from his Work task, you will need to create individual General Ends for each of your Human Activities and name the connector between them accordingly - in our case, Withdraw.

In the UI, when the user will do his task, in the Submit field drop-down list, he/she will be able to choose Withdraw or move forward.

Read more about Getting started with Live Manager.