Folks - I've been using Nextion for quite a while and always found getting acceptable looking fonts very time consuming (like many others). Thanks to those who have provided font editors in the past which were a help. Currently I don't think there are any editors available except the built-in Nextion font creator.
I've just spent a couple of days using the built-in creator trying to get fonts that fit with my screen design. I thought I'd makes some notes about what I found useful and hope it might help others.
A font that works quite well is Inconsolata (a mono spaced font (as required) with reasonable proportions (aspect ratio). I used fontforge (free software) to change some of the characters and then generated a new font which I added to the installed windows fonts. My new font could then be seen by the Nextion font creator. (When you install a new windows font you will have to shut down and restart the Nextion editor to be able to see it in the Nextion font creator.)
The Nextion font creator is a black box to me so I had to do a whole lot of trial and error experiments to see what works. One thing I figured out is that if for example, you adjust (move) one of the characters upwards in font forge (Transform -> move), it works OK on the Nextion screen. If however you move the entre character set up in fontforge, there is no corresponding movement of the font on the Nextion screen. I'm guessing the Nextion font generator looks at the range of heights in your font but not the actual height above the baseline - so effectively resets the baseline to where it was before you moved the character set.
Anyway, using fontforge does allow some 'editing' of Nextion fonts even though you have to do quite a bit of trial end error
Hope this helps.