There are scrips letting you look through visually similar kanji, such as the Item Inspector. I suggest you install it and do some extra cramming.
While not being the same thing, it inevitably also plays into similarities, (i.e. the basis on a common radical) is the keisei-script. During lessons it will give you an overview of kanji that have similar or dissimilar readings with a specific radical as their basis. That’s also helpful in visualizing the differences.