I'd really like Canvas to have the ability to augment Module items with explanatory text. My university currently uses Brightspace/D2L which makes it very easy to do this sort of thing and I'm surprised that it's not built in to Canvas. Right now the closest thing Canvas has is Text Header, which is different in several ways:
• It is not attached to a Module Item so when you move around one Module Item you must also move around its corresponding Text Header separately.
• Text Headers cannot be formatted (i.e. use links, insert images, even bold/underline/italicize)
• The input box for a Text Header lets you see about 30 characters at once, as opposed to the entire description you are trying to add.
Here's how Brightspace does it. This example is from a class with dozens of short video lectures, and putting descriptions like this helps students get a brief idea of the content of each video before clicking on it.