You can manage (i.e., create, update, delete) Pre-Conditions directly through Jira's native REST API.
The Xray REST API provides the following endpoints.
To view the Test associated with a Pre-Condition you need to specify the key of the Pre-Condition you wish to view.
To associate or remove a Test from a Pre-Condition, you need to send a JSON with a list of the Test keys.
To remove a Test from a Pre-Condition you need to specify the key of the Test you wish to remove.