There are two ways to rename an experience in Flex:
Renaming an Experience from the Flex Admin
Hover over the target experience tile
Select the options icon in the bottom-right corner of the experience tile
Select (Rename) from the contextual menu
Input the new experience name in the "Rename" window
Select Save
Renaming an Experience from the Flex Workspace
Navigate to the name bar in the top-left corner of the Flex workspace
Double-click on the current experience name
Input the desired new experience name
Press Enter on the keyboard
Updates to an experience name will be reflected in the Admin and Flex workspace, regardless of where you made the changes.