There is no option to edit legends with the Topographic layer. Maybe you could make a copy of your project and do some testing in that one to test your work around option you are referring to.
Copying a Project:
1. Click the File Menu and select Open Project. 2. You can answer No to making a project backup for this scenario. 3. When returning to the Project Selection, your current project name will be highlighted. Click the Copy project button. 4. Enter a name for the new project such as Copy/Test (your choice really). Password is optional, however, if using a password in the original project, it will copy the required password for this test project as well. Click OK. 5. Then select this new Copy/Test project and click OK.
If this project you can play/test of any work around options you may think would help you achieve what you are looking for. Once you find an option you like, then go back to the real project and continue.