Enable or disable graph grid

[Olondre]

I think the problem is changing a .rtf file to .css. See here:

Can I hide the LOWER left sidebar buttons?

It’s possible the css file isn’t plaintext (manually changing .rtf to .css doesn’t produce a plaintext file). In TextEdit, from the menu items Format > Make Plain Text, and then confirm it’s a .css file. That should do it. An easy to use, but powerful text editor alternative for macOS is TextMate.