I would like the same functionality for reviews as there is already for reviewing previous mistakes i.e. you can select what you want to review. You may choose characters(red cards) only or words (purple cards) or both.
The reasoning is character cards don’t have sentences and I could practice them on the train since I won’t combine it with speaking. Word cards have sentences so I can practice speaking while reviewing.
Hope this makes sense.
Upvoting this idea! Sometimes, I’d like to just review the dictionary items, or just review characters. The settings, at the moment, let us choose either random order, or in the sequence of {components, chars, words, dicts}.
I need the same. Coming back after 3 months off, it has tested my recalling capabilities with not so good outcome. I would like to be able to review just the first 30 or so components or characters until I progress to the level I was at, before the break. Then continue with normal reviews and lessons as per course schedule. Current review options do not let me go back to the start … 
Yeah, part of the motivation for the Review Order settings was to help with this.
I wonder if there is some sort of middle ground we can strike only tweaking the Review Order setting 
otherwise I can see a modified pop-up just like extra study, or an intermediary screen, perhaps
Do you mean a setting that allows you to choose to review words first then characters or vice versa? Similar to the settings already available where you can choose meaning or pronunciation first? If so, that is basically what I am requesting. Maybe not excatly the functionality as the review previous mistakes functionality, but it would do the same thing.
So for your current use case, the Review Order settings should have you covered – it prioritizes all characters before words. The sounds and components will come first before characters as well, though knocking those out before getting to characters may help build momentum 
As for prioritizing words over characters, or dictionary items over words, and more ordering permutations, we don’t have that supported at the moment. But I don’t see why we couldn’t add it 
Actually I’ve got it set to words first then characters but words and characters still come mixed. I thought that setting meant that a word would be shown before it’s single character if both were in the deck for that day’s review. The functionality I’m talking about is to be able to only do red cards, and then only purple cards.