Also in light of the disappearence of the summary page (which I would love to have back), would it be possible to have the “unburn” button appear directly somewhere in the page, when doing Extra Study for Burned Items?
Now it feels a lot like : “oh I got you wrong? See you never again!”
It would be more helpful (at least for me) if there was a way to choose which recent lessons to review and which recent mistakes to review.
Maybe adding a down arrow to expand the list of the recent lessons/recent mistakes so you can check off what you want to review.
I prefer not to use userscripts.
any other apps or sites you can recommend for further reviewing? i love the extra study mode and always use it but they disappear once i get the items to Guru. i was hoping to still review all the items from time to time before they get burned.
Smoldering Durtles on Android has a self study feature where you can study all levels. I use it on my phone and tablet and enjoy using it.
Could you create extra study for different JLPT levels kanji and words? It would be a great tool to review.
I am just adding my voice to what other people have asked for. Right now the Extra Study feature feels a bit useless. Reviewing 6040 burned items in one go just isn’t practical. I’d love something similar to the Advanced feature in lessons. If I could review…
…in one session, that would be much more useful!
When I started WaniKani I was just getting started with Japanese. This month I moved to Japan and I’m working towards the N2. I’ve noticed that with the recent WK levels (in the 40s) because my Japanese comprehension is better, I encounter ones I learn a lot when engaging in native content and remember them in no time. However, I can struggle with a lot of the level 20 ones because at that time I was looking at N5-4 tests and not seeing them frequently ‘in the willd’. Being able to effectively review each kanji and its associated vocabulary in one session would be immensely useful.
Please consider it! 
If the rationale for waiting for review is to improve memory („we wait until you are just about to forget them in order to recall them and tell your brain to make longlasting connections“ - to paraphrase), then why are extra study sessions offered with the pretext of „improving memory“? Which one is it? Should I wait to improve memory or include extra study to improve memory? Is having to wait a way to keep people subscribed to the app longer after all? 
Welcome to WaniKani.
I don’t think waiting for memory improvement is the right rationale at all, but when I went through old forum threads there was a lot of debate about it. Some people swear by better memory through waiting, but I don’t think there’s any science to back that up (and I looked).
Here’s the opinion of a newbie. WaniKani isn’t the be all and end all of your Japanese studies. The point of it is to give you kanji and vocabulary so you can get started with grown-up reading and not have to rely completely on furigana and dictionaries. You should be studying in other ways for grammar and listening and getting into reading when you can. So you will always come up against many of the words/kanji you learn here anyway. WK is paced to give you the least workload to remember the kanji and vocab until you start encountering them enough in the wild for immersion to take over.
tldr: if you have the time, do extra studies here or start other studies elsewhere. Don’t overthink it.
„ The goal of WaniKani’s spaced repetition system (i.e. our intelligent flash card system that adjusts its review timings to how well you know something––or don’t know something) is to give you a review right before you forget it. When you do that, it tells your brain ‚hey, this is important to remember!‘ As you answer your radicals reviews correctly, it will increase the amount of time until the next review.“
This is literally the e-mail I got from WaniKani
If it‘s about efficiency, as you say, why doesn‘t WaniKani give me the freedom of choosing for myself how fast to go?
You can complete in around a year, you can take a lifetime, or anything in between, so I’d say there’s a degree of flexibility. However WK strongly controls reviews by using a fixed SRS system that demands you wait for the reviews that count.
You get three free levels on WK to see if it suits. I suggest you spend two or three weeks trying them out. WaniKani is what it is, and whether you can live with that is up to you. If the general system is okay, you can tweak the web experience somewhat through applying user scripts or by using a third party phone app. If not, you can choose to tailor your own SRS program with Anki where you can tweak the timings and maybe use the cards from Kanji Damage or core 2K, etc. You can learn kanji meanings more quickly through the “Remembering the Kanji” (RTK) system, where (as best as I understand it), the readings are learned afterwards. Kanji Koohi might be worth investigating for a SRS system for RTK.
If you don’t like SRS at all, maybe WK is not for you. There are plenty of methods out there to pick from. You need to find what suits your learning goals best. Once you’ve found a route that suits you, get stuck in.