Davinci Resolve: How to easily add background-colour to text?
Use a Text+ for the title.  In the Inspector, go to the Shading Tab, and in the Shading Elements section, change the &quot;Select Element&quot; dropdown to &quot;4&quot; and check &quot;Enabled.&quot;  Change the color of the background from the default blue to black, and if you don't want the black boxes to split between characters, then change Properties-&gt;Level to &quot;Line&quot; or &quot;Word.&quot;
The numbered &quot;Shading Elements,&quot; in case you're wondering, are preset slots, where you can save combinations of settings for Fusion Text+ nodes.  A few of the slots are pre-populated with commonly used defaults like this, outline, and drop shadow, for example.  Multiple elements can be active simultaneously.
I'm using Resolve 17Beta9.  I know that R17 allows more of Fusion's parameters to be published in the Edit and Cut page inspectors, but I don't remember if this particular control was new to those pages in R17.  If you don't see the controls in the Cut/Edit page inspectors, and you're using an earlier version of Resolve, switch to the Fusion page, and they'll be available there.
If you don't want to repeat the styling steps every time you want another title to appear, you can save a template by dragging the Text+ clip (after you've adjusted the look) from the timeline to the media pool.  Then, dragging the template from the media pool to the timeline will instantiate a new title, with the saved look, and you only need to change the text.  There are other ways to do this when you want to re-use the same style across projects, but this method is the simplest.