Open a server action, don't edit anything, click on the Workflows tab on the left menu bar and it closes the open action. This shouldn't happen - I'm just trying to view more of the action on a small screen before I edit it.
This is actually by design. Single click opens the action in preview mode only. So when you click on other actions they are also opened in the preview tab.
Only when you make some changes or open the action in edit mode (by double clicking) then it will stay open till you close it.