Changing fade_fold_buttons to false makes folding arrows disappear for all other open tabs.

"fade_fold_buttons": false

to my user settings, and after saving, the code folding arrow appears for the settings file, but for all the other files open in other tabs, the folding arrows disappear. It's only a minor burden since any files that are subsequently opened will show the code arrows, so you just have to close the existing file and reopen it, but it would be a nice fix.