Use > Customize My Workspace > Set up My Workspace > Modify the maximum number of pages

How to Modify the Maximum Number of Pages

By default, up to 10 pages can be open at the same time. If you have multiple pages open, up to 5 pages are refreshed automatically (based on which pages were accessed most recently); any additional open pages are refreshed when you select them.

These limits apply both to My Workspace and Service Health.

This section describes how to modify these limits. Note that if you increase these limits, performance may be impaired.