Hello,
Unfortunately it doesn't seem possible to "duplicate" or "save as" an existing Guided Task as a copy. This means you have to create each new Guided Task from scratch, which is inefficient and very very time-consuming... even though some are meant to be very similar except for a few things to change in the Steps. For example: How to create a Contact / How to create an Account / How to create an Opportunity.
I have suggested adding this Duplicate function in the Microsoft Suggestions Box. Please vote for it to appear at the top of the suggestion list here: https://experience.dynamics.com/ideas/idea/?ideaid=7e91a1cb-e942-e811-a822-0003ff68bbc0
Thanks!