Thank you, @Abroxus for making a post on this topic as well. They have posted a solution on their post.
I accidentally clicked on a new feature on the mobile app that changes your avatar’s position on the website and I don’t know how to reset it to default. How do I do that?
As of right now, I think there’s no way to revert it to default. I’ve been looking for a fix on this, and your DevForum post seems to be the only close thing to a post made on the situation. I would recommend suggest it in a feedback support ticket, or get somebody with higher influence to report it on other social medias where Roblox’ staff actively look. It’s a shame nothing can be done about it right now, but hopefully there will be a fix in the future.