Datacenter API: Can you create a Test Plan or update a Test Cycle?

We have users that are looking to link Epic/etc to Test Cycles. But while you can do this manually I can't seem to see it in the API? Also, can't seem to update a Test Cycle via the API only create one.

Then I saw that we can update a Test PLAN to include links via API, but can't create a Test Plan via the API.

Am I completely missing a section of the API?

https://support.smartbear.com/zephyr-scale-server/api-docs/v1/