aprilnya parent
Yes, deleting your encryption keys every time you close the end to end encrypted chat app is definitely a great idea
I know nothing about any of this and I am surprised to learn that something that is apparently considered to be permanent is stored in something as ephemeral as a browser cookie, and then causes problems if deleted. At least this is how I understand the exchange above.
Any web application really has access only to "ephemeral" storage like cookies or localStorage when used in this manner (you could be cleaning your localStorage for every session too).
Switching to localStorage would help things, but until they do, you can avoid the known failure case for Element Web by not doing that.
Obviously though, they need to figure out a way to reestablish encryption when the keys are gone, as long as you are willing to accept no access to history, or keeping keys encrypted server side.