Blocking 3rd party cookies has so much merits in terms of security but it also has a flaw, some websites might not work.
in Edge insider settings page it says:
"Block third-party cookies
When on, sites can’t use your browsing activity across different sites to personalize ads. Some sites may not work properly."
I have it turned on regardless because for example when I go to YouTube.com, I only want youtube.com to save cookies in my browser, not facebook.com or google.com
3rd party cookies are mostly used for tracking your online activities.
so to tackle the issue that comes with blocking 3rd party cookies, which is some websites might not work properly, I Suggest to add this new feature to the Edge insider browser:
Delete Only 3rd party cookies at exit
so with this method, you allow the website to set their 3rd party cookies, thinking they can track user's activity all over the web, but as soon as the browser is closed, all those 3rd party cookies will be deleted and only the 1st party cookies (main cookies) stay in the device, retaining user's login.
I haven't seen it in any other browser.
I really hope developers see this and add it to the Edge. will be a great addition to the Tracking Prevention system, make it robust.