ttb.user.js

// ==UserScript==
// @name        Bingosync Custom Input
// @author      mathgeniuszach
// @description Enables you to paste lines of text from a spreadsheet or list into Bingosync.
// @version     1.0
// @match       https://bingosync.com/
// @run-at      document-start
// ==/UserScript==

window.addEventListener("DOMContentLoaded", () => {
  json_box = document.getElementById("id_custom_json")

  if (json_box) {
    json_box.addEventListener("focusout", () => {
      if (!json_box.value) return
      if (json_box.value[0] == "[" || json_box.value[0] == "{") return

      json_box.value = JSON.stringify(json_box.value
                                      .trim()
                                      .split(/[\n\t]+/g)
                                      .map(e => {return {"name": e}})).replace(/,/g, ",\n")
    })
  }
})