@mahoneycm Should the base branch on this bb be release-3.9.0?

suggestion:
I am thinking that we should add some additional notes about this setting to responsive-variants.html.

1. Suggesting we update the section to include a sentence like this:
   "Additionally, you can add custom breakpoints to your project by configuring the $theme-utility-breakpoints-custom setting. Learn more about the breakpoint settings on the Settings page."

   Before:
   

   After:
   

2. Additionally, it might be a good opportunity to add a yellow site note here that warns users that each breakpoint that is turned on makes a sizeable impact to the compiled CSS. (right now, adding a new breakpoint adds about 50kb to the total file size). Here is a possible draft note (this will probably need to be cleaned up):

   "Note: Turn on only the breakpoints you need in your project. Each enabled breakpoint will increase the size of your compiled CSS by a significant amount. To improve performance on your site, turn off any unused breakpoints."

Update: I'm going to move my suggestions to enhance responsive-variants.html to a separate PR so that it doesn't hold up the release. We can evaluate it independently as a follow-on if needed

Update to the update: I opened #2852 for this proposed addition.