If you are able to install and set-up the Stylus browser extension and write your own script you should have no problem setting up and using any of the WK user scripts. Somewhere here in the forums there is a post/thread with tips on getting started with user scripts for WK.
A very quick overview:
Install the Tampermonkey browser extension. Home | Tampermonkey
Jump over to Greasy Fork https://greasyfork.org (repository for user scripts) and search for “WaniKani”, which will show all the WK user scripts folks have written. There are many dozens of WK scripts.
You will want to install the WaniKani Open Framework first (most scripts rely on this framework). Then any particular scripts you would like to use. Installing a script is as simple as clicking the script in the list to go the script page and then selecting the “Install this script” button.
Most of the scripts, especially the ones that are used by a lot of folks, will have a discussion here in the forums where you can find details about the script and post questions or suggestions. Generally such discussions were started by and are monitored by the script developer/maintainer.
The API and Thirdparty Apps category is where you will find them. API And Third-Party Apps - WaniKani Community