Reverse engineering expert, Jane Manchun Wong, has had her name appear in the news numerous times during the course of the last twelve months, such as Snapchat's testing of "Status" for checking into locations and showing your activities and Spotify's internal trials of a new "Social Listening" feature that would enable users to listen to music together.
Now, it appears that Wong has unearthed another gem, this time focussing on Twitter's progressive web app (PWA):
Twitter is testing "Customize your view" UI, allowing users to change theme color, shades of dark mode and font size!— Jane Manchun Wong (@wongmjane) June 28, 2019
This will replace the "Dark Mode" sidebar toggle pic.twitter.com/2UDkmVG6W8
From the screenshot in the tweet, users will be able to configure font size, theme color, and background shading courtesy of a new user interface called "Customize your view". At least in the Windows 10 Twitter app, this interface is perhaps a refined version of the current arrangement of options shown under Settings > General > Display.
Twitter's PWA solution currently powers the user experience on its website as well as the Windows 10 and Android apps so, as with any leak, it remains to be seen if this makes the cut in terms of public release.