CSS Class for order note ?

Hi, samuelfox, the following documentation should assist you with this:
https://docs.woocommerce.com/document/tutorial-customising-checkout-fields-using-actions-and-filters/#section-1

and https://docs.woocommerce.com/document/tutorial-customising-checkout-fields-using-actions-and-filters/#section-2

You will want to checkout the woocommerce_checkout_fields filter.

Ian @plantprogrammer, thank you so much for helping out here!

@samuelfox, we haven’t heard back from you in a while, so I’m going to mark this thread as resolved. I do hope Ian’s answer helped you.

If you do need additional assistance, we’ll be here if/when you’re ready to continue.