In Preferences -> Formatting, I set the main text to Menlo 14 but when I create new texts, the top line is mostly off the screen. Same for full screen view. The top line doesn’t appear correctly. Just wondering if I need to set some other option or it’s a bug?
I’m not seeing this, so there must be some other settings applied to the text other than just the font. Try resetting the text to “Body” from the formatting presets (left-most button in the format bar), then apply Menlo 18 again to see if that clears it.
Also check your line-height settings. I can reproduce this look with some bizarre settings, like 0.6 multiple / 18.0pt inter-line spacing.