Is there any way to have Metamask use, for instance, the mainnet in one Chrome tab and Kovan in another? Thanks!
In the short term, there's no way to do this, in the long term, MetaMask is interested in doing this, but it's probably going to be a while, I wouldn't be surprised if it was more than a year out.
One way you can work around this in the meanwhile is to use multiple Chrome profiles, and you can have a different instance of MetaMask on each profile, even a different seed phrase, which can be very nice for using multiple networks at once.
No, this is not possible, unfortunately.
The way I debug is to use MetaMask on the main network in a normal Chrome tab, and use a local Parity node on a testing chain in a Chrome Incognito tab.
This way you can still have two Chrome tabs on different Ethereum chains.
I hope this helps :-)