after wiping the entire css style i've been working, i tried to open the css menu. But the menu won't open, and whenever i click the css menu, it renders other menu unable to open such as preference, statistics, tag manager, etc. A simple reload or restart would activate other menu, however, the custom css menu still won't open. The log has been telling me that: No command registered with the application for command win-menu.
I tried to renew the config.json file to no avail, in case the configuration has anything to do with the error
CSS style would be okay again

Thank you so much 😄
Hmm … is the empty CSS-file present in the application directory?
I confirm this on macOS 10.14.5 with 1.6.0beta4. It's even worse: none of the file-menu dialogs open after emptying out custom css: preferences, manage tags, custom css — nothing. It doesn't start working after a restart either. Zero-bytes custom.css disables all dialogs in the app. To me, it's pretty serious.
After typing just 1 letter into the custom.css and restarting the editor, dialogs are working again.
Well, it's not that bad, because the file is always preset with a comment, and as the dialog says "modify at your own risk" ;)
Nevertheless, I suspect it has something to do with the fact that in Electron 8 they changed the underlying Node version to a newer one, which broke fs.readFileSync to return a Buffer instead of a string, as before. Maybe it has something to do with this. I'll get to it in the next few days ^.^
well, i haven't checked if the CSS-file is in the directoriy, I reinstall zettlr and now everything is good. You are right 😄 i modified it and suffered the risk, but I couldn't be happier for being able to tinker the css. It is the best experience i've got with zettlr these past two days. Anyway, thank you for your help 😄
Aaaaand here we go!