I'm kind of the in same boat as you. I'm a planner at an engineering firm, and trying to move into design work as well. I found these free online classes looking for design training. I linked to the last in the series. If you look at the prerequisites, it lists all of them. I haven't completed them yet, as I'm trying to get my work to pay for a Planetizen membership.
http://www.ucl.ac.uk/lifelearning/courses/urban-graphics-mapping-gis
If you don't mind paying, Planetizen has a ton of classes and training programs.
https://courses.planetizen.com/
https://courses.planetizen.com/track/urban-design
I also found this course very helpful when making exhibits and presentations. It's a basic intro to graphic design class.
https://www.coursera.org/learn/presentation-design/home/welcome