My first suggestion is to install the Item Inspector
It will allow you to look at your leeches and get pop-ups for similar looking items AND quiz you on similar looking items (with the help of the Self-Study Quiz).
In addition, it allows you to define how similar you want them to be (and thus change how many similar items gets included in the quiz or on lists).
I also recommend the Shin WaniKani Leech Trainer as it’s specifically aimed to target interference (confusion from similar items)
If you want more inspiration on how to tackle leeches, you might wanna have a look at my study log. 
*ekg’s leech battle blog - a study log of sorts
Good luck with your studies! ^>^
