The new Admin Portal in Pega 8 is good but one big difference to it from how SMA was used in previous versions is that you can't have Admin Portal opened the same time you're working on Dev or App Portal.
I think actions performed in Admin Portal are closely tied to actions and settings that are configured in Dev Portal and when you have to work on an Email Channel, Listeners or anything else or that sort you have to keep switching between the two portals.
It would be good to see Admin Portal open in a new tab or window in future releases.
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