I use the app called Ringotan, it’s nice, because it supports WK by default
If you have WKOF installed (if not, go to here), you can just open up your developer console (Ctrl+Shift+I on chrome), and paste in the following piece of code:
wkof.include("ItemData")
wkof.ready("ItemData").then(() => {
wkof.ItemData.get_items({wk_items: {filters: {item_type: "kan"}}}).then((kanji) =>
console.log(kanji.map((k) => k.data.slug).join()))
});
It results in something like this:
