What is the best/suggested way to learn just the radicals and Kanji that are also radicals with renshuu? At the moment, I searched for Kanji with the word "radical" in their meaning and I created a lesson based on that. Is there a better way?
Well, currently you cannot study radicals in the sense that they are entirely separated from kanji. However, if you have a list of kanji characters from any of the kanji lessons on the site, you can study the radicals associated with them. When you start the quiz, click the little settings button to open up the question settings. You can turn everything off except for radicals - and then you can choose from radical only questions (shape -> name, etc.) for the radicals that appear in that list of kanji.
I agree - I would like to implement it in the future, but it is unfortunately unavailable at the moment. I do appreciate the comments and interest, though!
Well, I learn by practice. Staring on definitions doesn't help me much. That said, the nuthatch list is a great source for building a lesson here in Renshuu. It would be ideal if there was a "prerequisite mode" when learning kanji. For example, if I put a kanji on my list and the prerequisite mode is enabled, then before I get quizzed on the actual kanji, I will first be quizzed on the associated radicals/radical kanji (until a sufficient mastery level is reached) that are part of the kanji I want to learn before the actual kanji is introduced. Just tossing an idea.
For example, WaniKani is built to first introduce the radicals and then the kanji and it works pretty well for that. However, Renshuu is more comprehensive and has a better/more flexible goal management system, therefore, I think Renshuu is best in the long run.
I run the site on my own, so while I do not have the resources to implement everything, I am someone you can talk to directly any time you have ideas, complaints, criticisms, etc. It might not be an affirmative answer, but I will answer you about anything you are thinking about related to renshuu!