I was in search of the same solution - wanting to be able to learn to write the kanji as I learn them here on WaniKani (always in search of that ultimate japanese learning solution with WaniKani at the heart).
Note! I’m presuming I’m allowed to post this because it’s just strings of Kanji, but if it goes against the community rules feel free to delete.
For anyone else wanting to add the WaniKani kanji sets to Kanji Study, I have created importable txt files (pulled from the items list on wkstats) you can use to import a custom group on Kanji Study. I have split them into groups of 5, and a giant file of 1-60, depending on how you want to use them. I find groups of five is good if you want to split them out further in KS or create smaller, more manageable groups.
Levels 1-60
https://nofile.io/f/C7o6nZACqjY/wk_1-60.txtFor 1-60, the imported levels in KS will match those on WK. It takes about a minute to import.
Split levels
https://nofile.io/f/JTuzN0TCkhW/wk_1-5.txt
https://nofile.io/f/GfKD24EqaKm/wk_6-10.txt
https://nofile.io/f/gwOgjAU6SVP/wk_11-15.txt
https://nofile.io/f/SOKMYsq7M42/wk_16-20.txt
https://nofile.io/f/vxYKB2b8w4C/wk_21-25.txt
https://nofile.io/f/sMNWB6vzqQO/wk_26-30.txt
https://nofile.io/f/NSh0d7BeGeO/wk_36-40.txt
https://nofile.io/f/Uc47D4vx33Y/wk_41-45.txt
https://nofile.io/f/GuHg0MDE283/wk_46-50.txt
https://nofile.io/f/NDD8460PNmV/wk_51-55.txt
https://nofile.io/f/7Zr4UJEdHNZ/wk_56-60.txt
The above links no longer work - please use @normful’s updated post!
Save to your device, then create a new group (or groups), click add, import from file…
Hope this is helpful to you all, and thanks to WaniKani and KanjiStudy!