Hi @Chriss Haddad,
I refer to the Chrome document which you shared in the original post. Its shows an option to make the extension Private. It does not contain any information about publishing 2 extensions.
I refer to the Microsoft document and got the information below.
Ref: Provide Availability details
So, if you select the Hidden visibility then you could use extension for testing purposes.
The document does not describe whether you could publish 2 extensions, one for public and another for testing.
At a time, you could upload single package. For testing purposes, I would suggest you publish 1 copy of extension and make it public.
Then repack the extension again with the different extension ID. Now you have basically 2 different extensions. You could publish the extension that you repacked and make it hidden.
Note: You would need to test the extension locally to make sure it does not have any errors. If it contains errors, it might fail the validations step.
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