While usually the workflow proceeds from the top to the bottom, you can have it jump to any place in the workflow by using the "Then Run This Stage" option in a workflow stage, in the "Other Settings" section.

When you set this, then at the end of that stage, once it is processed, then the flow will continue from the selected stage. The script in that stage (if any) will run, and the options below that stage will be presented to the specified users.