Hello Tim,
I think, suspended workflows do not affect the system because there is a description in workflow section like below.
A Suspended workflow can occur when the incident closes before the workflow completes. Reopening an incident resumes the workflow. You can permanently terminate a workflow if it is suspended and you do not plan to reopen the incident.But if you already want to terminate them all periodically, you could write a script which uses SOAR rest functions and could be scheduled in cron. You need to use below rest endpoints.
To get workflow instances

To terminate workflow instances

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Burak Karaduman
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