Ok, I finally found it. You have multiple takes, and when your project is opened the “mixamo.com” take is selected. If you select the “Main” take you will be able to edit all of the Attributes parameters. I haven’t used the Takes system before so the details of it are beyond my knowledge, but since you are obviously using it hopefully you’re more familiar with it.
(edit: adding a take locks the current settings but which can be overridden with the context menu as I described in the previous response.)

