Is it possible to display a page title instead of page URL in Behavior flow?
Nope. Not unless you save the Page Title in a Custom Variable and then change the view from Landing Page to Custom Variable.
This is at best a hackjob, and I'd rather work on Creating a better Content Grouping and changing the view from Automatically Grouped Pages to the custom Content Grouping.
I have never run across a setting for that.
In general, Google Analytics doesn't record page tiles. Other reports such as "Site Content" show URLs rather than page titles as well.
Seeing human readable data in Analytics is one reason that sites like this one use a "URL slug" with the title of the page in the URL:
In general, you should have URLs that are both descriptive and as short as possible.