This is generally true of every application that handles sensitive data. Unless you explicitly clear that memory, it's likely to hang around forever.
For example, here is a 2019 writeup from KeePassXC with similar notes: https://keepassxc.org/blog/2019-02-21-memory-security/ - even though they explicitly clear sensitive data, there is still a window of opportunity.
During my time working on confidential computing, we had a variety of demos showing similar attacks against lots of different datastores, scripts, etc. That's just how computers work and your options are very limited if this is part of your threat model (imo just confidential computing and, if you can handle the performance hit, fully-homomorphic encryption).
Windows already has a secure kernel credential store, they could move the Edge password store there with a bit of effort, minimize the splash damage when you retrieve a single password to send over HTTP from the regular user space.
> Credential Guard prevents credential theft attacks by protecting NTLM password hashes, Kerberos Ticket Granting Tickets (TGTs), and credentials stored by applications as domain credentials.
> Credential Guard uses Virtualization-based security (VBS) to isolate secrets so that only privileged system software can access them.
https://learn.microsoft.com/en-us/windows/security/identity-...
This only works if credential guard has implemented a way to build a subsequent token/value from that secret. For things like basic auth the secret would need to eventually hit the userland process that needs it in some shape or form to then embed it in the HTTP payload which is plaintext.