English makes no sense.

Too true!

Isn’t “blend” related to light?

You can use blend for anything, especially if you’re creating a mix of two original things. And you could mix light too (you have things like mix() for colors in CSS).

In cooking, I would call something you use to mix dough a mixer, and something you use to make a smoothie a blender. I guess there are some subtle differences in “feel” but the words are almost interchangeable.

The fact that you used a bulleted list to describe what you like about Workflowy basically tells the whole story