In the Mac app (and iPad) I feel like always defaulting to the Discover tab is a bit annoying. I totally understand why you want to start users there in the beginning because you have a lot of discovery features there. But once the user has been using the app for a while I expect they generally would prefer to land in the Designs tab.
So my gentle suggestion is to remember across launches which tab the user was last in and restore to that point instead of always landing in Discovery. I think that would be a good balance of enabling new users to discover features and helping the workflow of folks who have been using the app for a while. I doubt you would ever restore to the settings tab but the other three seem just fine.