Flanges, like Sheet Metal cuts and faces, have now been transitioned to the Properties panel interface with the Autodesk Inventor 2025 release. As an Instructional Designer and Instructor, I have to say I really like it and find it very intuitive; however, it likely will take some getting use to.
I created the following video to help you out! Please take the time to give it a watch and if you are a brand new user you may want to consider purchasing our Autodesk Inventor Sheet Metal Fundamentals learning guide to learn even more.