To enable categories, make sure you're using the Default inbox style, then click the gear icon and go to "Configure inbox." In the overlay that pops up, select the tabs you want to use and click Save.
4. Use Personal Level Indicators
As we mentioned earlier, when you see a little yellow marker next to a message, you know that message is important. Conversely, a clear marker denotes that message is less urgent. But those markers can tell you even more if you enable Gmail's Personal Level Indicators. This feature will place arrows inside that marker to let you know whether a message was addressed to just you (single arrow), to a group (double arrows) or a mailing list (no arrow).
To enable this feature, click the gear icon and go to Settings > Personal level indicators, and select Show indicators. Click Save.
5. Customize the left navigation
If you're using labels to organize your content--and you should be--you can make them even more useful by customizing the left navigation bar to provide direct links to them. Gmail provides three display options for label links: "Show," "Hide," and "Show if unread." The last is probably most helpful for restoring sanity to your inbox, as a label link will only show up in the left navigation if it contains a message you haven't opened yet.
To customize link settings for each of your labels, click the gear icon and go to Settings > Labels.
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