This is 14 tracks wide, maximized on a 1920x1080 screen. It would sure be nice to have them just enough smaller to use the empty space on the right for 2 more columns.
Are you looking to monitor inputs across all your channels during recording? If so, the “Recording” view (Alt-R) lets you see signal all the available hardware channels. I’m pretty sure that feature landed in the 8.0 release, if not earlier.
Alas not on your screen. It doesn’t fit 16 in a single row (try with an image editing tool and your screenshot). There could be at most 15 and Ardour always uses an even number of meters per row, so you get 14.
You could try to decrease UI scaling in Preferences > Appearance > Size/Scale (and restart the engine to that the recorder gets updated):
Here I can fit 16 tracks at 100% font scale on a full-HD screen.
At some point during the 8.x release cycle we start using a bundled font (ArdourSans) for the entire GUI so that look and feel are more consistent. Prior to that the default desktop font and desktop font size was used. That may explain why it’s different on your system.