Recommendation for where to start learning how to design

Well, you are already ahead of the game. You still need to learn a 2D vector editor. No matter how accomplished and creative you become in a 3D CAD program, at times you will want to add something only a vector editor can accomplish. That said, I believe there are tutorials in the training matrix for Fusion 360. CAD programs require a lot of programmers to write, improve and maintain, therefore they can be pricey if they are not critical to your business. There are free versions of many, but they come with tradeoffs, like making your designs public. As a woodworker you may want to consider combining the two. While using the thin materials common to lasering with a traditional router table and table saw could be dangerous and a little more difficult, maybe make a router table and jigs for a Dremel tool? This could open up miter joints for you without the time and imprecision involved in using the laser and a grayscale engrave pattern. Or taking it the other way, quickly make unique router jigs for your traditional woodworking.