SEOPressor is a bit of a secret weapon. We use this alongside our Yoast SEO plugin but use the features separately. This plugin gives the ability to do multiple keywords along with tying right into the recommended content.

It also auto-decorates text in your content based on the keywords you choose. It will suggest keywords to use based on the keyword you entered. The plugin also has the ability to add rich snippets of all kinds. Some good features I honestly wish Yoast would adopt.