How to Globally change Bootstrap Theme via a custom.scss

Is there documentation or video illustrating how you can GLOBALLY redefine Bootstrap 4 fonts, colors, etc…? In Pinegrow (heresy, I know) you could easily create a “custom.css” file. I want to know if there is any feature in Wappler to accomplish the same. Using a custom.css file immunizes me from future upgrades to Bootstrap. Thank you in advance for any support or guidance on this matter.