I had this idea after reading this one:
https://connect.mozilla.org/t5/ideas/shortcut-for-different-profiles/idc-p/6317
In case you do not know what I am talking about, please check out this article explaining about guest mode (there's also pictures showing how it works).
In Edge and other Chromium-based browsers, through guest mode, it's possible to easily create a temporary profile that doesn't enable the privacy features of private mode, therefore potentially improving compatibility with privacy unfriendly websites, and allowing the use of a temporary history (as opposed to none in private mode). Also, in guest mode, all extensions are disabled, which is not always the case in private mode.
Overall I think it's a very useful feature, so please upvote this Idea!