How do I view all cookies in Opera - including the one storing the Google Channel ID?

Question

It seems currently impossible in Opera to view all cookies including their values. For instance, google (via its domains google.com, gstatic.com, googleapis.com, probably youtube.com, etc) sets some cookie named Channel_ID with a certificate or signature of type ecdsa_sig. This is about everything Opera will tell you about that.

Failed attempts:

• Settings -> Cookies -> All cookies and site data: Will show a list of cookies including the Channel_ID cookies, associated with their respective domains. Unlike for other cookies, the content is not displayed (only domain, certificate type, and creation time). It will give you the option of deleting this cookie.

• Opera dragonfly (CTRL+Shift+I -> Storage -> Cookies): Will only show cookies associated with the website that is currently open. Since gstatic.com and googleapi.com etc are not website domains, they will not show any cookies. For google.com etc. the Channel_ID will be omitted.

• Going through the Opera cache files: These are on Linux ~/.cache/opera/Cache/* (on Mac probably the same, on Windows probably C:\Users\<UserName>\AppData\Local\Opera Software\Opera Stable but I do not have access to either a Mac or a Windows system). It does not turn up anything related to ecdsa or Channel_ID; neither with cat and grep nor with hexdump -C and grep

• Browser Extensions ("Cookie Editor", "Edit this Cookie", "Flag Cookies") are not of any help and appear to be mere frontends for what you can have in Opera dragonfly (CTRL+Shift+I -> Storage -> Cookies)

How do I view the value of the cookie storing the Google Channel ID, presumably an ECDSA (Elliptic Curve Digital Signature Algorithm) certificate or signature? Or am I somehow misunderstanding the nature of this cookie? Or are there more cookies like this and it is actually quite common to not be able to see a value of a cookie?

Software is Opera (v. 52.0.2871.40) on Linux (kernel 4.15.15)