A tip/info.
Found that in Arduino IDE v 2.3.3 using a font in the Editor with programmers ligatures can be done.
Open the Advanced settings (cmd or ctrl-shift-P):
Search for "open settings"
Select "Preferences:Open Settings (UI)"
Search settings for "ligatures"
Find:
Editor: Font Ligatures
Configures font ligatures or font features. Can be either a boolean to enable/disable ligatures or a string for the value of the CSS 'font-feature-settings' property.
Select "Edit in settings.json"
In settings.json", find the line:
"editor.fontLigatures": false,
and change it to
"editor.fontLigatures": true,
This assumes you have set as your primary Editor font one that contains "programmers ligatures" such as JetBrains Mono or Fira Code.
If such a font is installed, change the Editor font list to use it. To do so, in the same settings.json file, search for editor.fontFamily: and edit it so the font you want is listed first. It should look something like:
"editor.fontFamily": "JetBrains Mono, Menlo, Monaco, 'Courier New', monospace",
Going further, you can also specify the font used by the integrated Terminal by searching in the settings.json file for "terminal.integrated.fontFamily" and specifying it first in the list there. For example:
"terminal.integrated.fontFamily": "JetBrains Mono, Menlo, Monaco, 'Courier New', monospace",
Note that ligatures cannot be used in the Terminal.