As the title says, how to hide the backlog issues on the Xray Cloud

Step-by-step guide

That backlog is generated with a JQL query on the settings of the Backlog. You just need to create a query that filter all the issues that you have available on the project.
For that you go to:

  1. Project-Backlog:

  2. On the top right corner, press the tree dots button and board settings:
  3. Now, press the Edit Filter Query:

  4. In there, create a jql query something like this, just adding the issues that you use in the project in order to hide them:

    project = <PROJECT NAME> AND issuetype not in (Bug, Test, "Test Execution", "Test Set", "Test Plan", Story, Precondition, Improvement, "Sub Test Execution")

  5. Save and with that you shouldn't have no more issues on the backlog!