What projects learn for software role?

In the past, I have successfully undertaken projects that naturally interest me to become proficient in embedded electronics to run a successful consultancy. I write a lot of bare metal programs in C and script in Python. I would like to move towards a (maybe backend) software role (over the next couple of years) and so looking for personal projects I could undertake in the Node.js/JavaScript area. Could anyone suggest anything or a direction that will give me strong experience relevant to popular industry projects? Many thanks!