I’ve been using a Chromebook to code for my Computer Science college classes since last January. It works great. But recently I had to flowchart an algorithm. Draw.io is a great web-based app for nearly any type of diagramming needs.
Using OneDrive, a NAS, or some other cloud storage with your Chromebook? Chrome OS 75 will make it easier to access that data by mounting it to your Files when you install the Android app for those services.