You can use OOTB activity: jumpToTask to jump between the assignments within the existing flow. PFB detailed explanation.
1. I have configured a process in a stage with three assignments.
2. In the post processing activity of the assignment1, add the activity:jumpToTask which accepts the current process and the step which you want to move. As I want to skip the assignment2, I am giving the parameter as assignment3 and the current process name.
3. Run the case now. Once the assignment1 has been completed, it moves to assignment3 and skips the assignment2 :)
4. PFA document for reference. Please mark this post as answered if it suits your requirement.