When Jane Foster became the Mighty Thor in Marvel Comics, her costume as the new God of Thunder featured a particular element that was pure genius. While she may have become a Valkyrie in the current Marvel Comics, Marvel's War of the Realms event saw Jane briefly becoming a Thor once more. As such, Marvel artist Esad Ribić speaks to her costume design in The Art of War of the Realms, especially her unique dual capes and their unique purpose.
After Nick Fury rendered Thor Odinson unworthy in the 2014 Original Sin event, Mjolnir sought out a new hero to wield it, eventually calling out to Jane Foster and granting her the power of Thor. This included a brand new costume as she became the Mighty Thor, wearing a helmet to mask her identity which was largely a secret for the majority of her tenure as the next God of Thunder. However, the helmet wasn't the only new piece to her costume, ultimately proving itself to be a brilliant addition.
In Marvel's The Art of War of the Realms book, Esad Ribić speaks to the fact that Jane Foster's Mighty Thor not only has a classic red cape attached to her shoulders, but she also has a second smaller cape around her waist. Apparently, this is to better convey the effects of any inclement and stormy weather the God of Thunder might have been causing, as well as just simply flying thanks to the power of Mjolnir. According to Ribić's explanation in the book:
"There are elements of Thor that you have to have... I added another cape around her waist so she has two capes. You cannot believe how helpful it is for the Thor character to have a cape, because that gives you physics - it helps you to express the movement or the wind."
While Jane hadn't been the Mighty Thor for some time, the War of the Realms event did she her briefly return to the role to assist the Odinson as part of a team of Thors who assembled to save the Ten Realms. Likewise, she also had a small return to her Mighty Thor costume when she was tempted to regain her power during Marvel's more recent King in Black event. As such, it certainly seems as though the Mighty Thor costume keeps popping up from time to time in the Marvel Universe, and will likely continue to do so considering Jane Foster's upcoming debut as The Mighty Thor in the MCU with Thor: Love and Thunder.
While it's not as necessary for a live-action version of the Mighty Thor to have that second cape to help convey movement, it would still be a nice feature. Not only does it serve to further distinguish her look beyond the classic Thor look, it also just looks really cool. Whether it's in the comics or on the big screen, here's hoping Jane Foster's second waist cape as the Mighty Thor sticks around in the Marvel Universe.