When a ticket is worked on, the ticket goes step for step through the workflow.
There is an option called "Redo Step" to jump back to an earlier step which will be redone then. To do so, just select the earlier step and press the "Redo Step" button.
In this example we are currently at step 5 while step 3 shall be repeated (and therefore step 4 and 5 also becuse in the repeated step a change could have be configured).
Here, in step 5 the step 3 is selected and shown (read only).
After having selected the step, press the "Redo Step"button.
So the ticket goes back in the workflow to the step selected (in this case back from step 5 to step 3).
BUT - this sometimes doesn't seem to work
In the upper example, step 2 is shown with a "skip" sign. This sign is shown if the step of the workflow has been skipped in this ticket. Due to this, a "Redo Step" can't be assigned. At the first glance, it seems to be strange that this step can't be selected, but with a second look it's quite logical. Btw - if a ticket using other conditions is going through the step, a "Redo Step" for this step can be configured later on. In this case, the "skip" sign doesn't show up in the ticket.
Lesson learned:
The option "Redo Step" can be used to go back to any step the ticket has passed before.
If a step has been skipped, going back to this step using "Redo Step" isn't possible.