Chrome extension from cloudHQ lets you turn your custom labels into tabs
If you use Gmail, you need the free Chrome extension Gmail Tabs.
It turns your cluttered hard-to-see Gmail labels in the sidebar into tabs above the Google-standard tabs along the top of the inbox just below the search bar.

If you’ve ever missed an important message despite meticulously curating your Gmail labels like your life depended on it, this is for you.
The extensions free version lets you create custom tabs from your labels (see above) as well as create tabs for frequent inbox searches and complex inbox searches. A premium subscription for $2.99 adds email and phone support if you need it.