on learning things "again"

When one "learns" something, the knowledge often gets thrusted upon in a hurried setting that does not let the learner fully grasp it: they seldom look deeply into it, or do not see how it plays out beyond that setting:

When you have to learn something like "JavaScript" at work, you learn what you need to know to get the job done; you can't read the whole JavaScript book and grasp everything about every thing built-in to it. It is much like working with red and blue, while not seeing yellow and green, then saying that you know the whole rainbow!

Filling in the knowledge gaps

When a slow day happens, however, that becomes the time to look at the "knowledge gaps" of something:

This goes for anything and not only things linked to work: let's look at English! Even now, I keep learning eye-opening things about the most beginner English words, such as their roots, their links with other tongues, their other meanings, "slang" ways to say things, etc.

So, "learning things again" might not have to mean "doing something again", but maybe it could mean "doing something more in-depth"?