I’m not sure if this has any help to you. But how our company’s software uses cookies is by only having one cookie that contains JWT token with unique client id. Then we tie everything to that client id, like authorization when user is logged in. So instead of using multiple cookies as such we only have one cookie that identifies the browser. Instead of cookie you could also use local storage then send that in LiveSocket params on connect. Of course that is not as secure as http only cookie.
Edit: Actually I’m not sure if you are even using LiveView 
But maybe Phoenix Channels or what ever you are using could also support this.
