I would like to suggest adding an option to pick whether you want only Vocabulary or only Kanji to appear first in reviews. That is because if a word using a kanji appears first and you fail it, then you will remember the reading/meaning and complete the kanji entry correctly, falsely "upgrading" the kanji's level unless you choose to fail it unintentionally.
For example, if all the kanji appeared before the vocabulary, then you can practice knowing the readings/meanings of the kanji alone first, making it clearer whether or not you've failed the kanji/vocabulary because you don't remember the reading/meaning rather than completing it correctly because you've seen the kanji's reading/meaning in a previous vocabulary review entry.
I would like to suggest adding an option to pick whether you want only Vocabulary or only Kanji to appear first in reviews. That is because if a word using a kanji appears first and you fail it, then you will remember the reading/meaning and complete the kanji entry correctly, falsely "upgrading" the kanji's level unless you choose to fail it unintentionally. For example, if all the kanji appeared before the vocabulary, then you can practice knowing the readings/meanings of the kanji alone first, making it clearer whether or not you've failed the kanji/vocabulary because you don't remember the reading/meaning rather than completing it correctly because you've seen the kanji's reading/meaning in a previous vocabulary review entry.