Userscript to add a delete issue button in the issues page. It opens the issue in a new tab, delete it, and auto-close the tab (sometimes not working). There's also a button to delete all issues in the current page, which opens all the tabs at once. Also works for discussions. BEWARE that deleting issues is not reversible!

GitHub Delete Issues.user.js

// ==UserScript==
// @name         GitHub Delete Issues
// @license      MIT
// @version      0.1.0
// @description  Adds buttons to easily delete issues
// @author       bluwy
// @match        https://github.com/**
// @grant        none
// ==/UserScript==

;(async function () {
  'use strict'

  if (location.pathname.endsWith('/issues')) {
    // Add delete button to each issue row
    const issueGroup = document.querySelector('div[aria-label="Issues"]')
    const issueRows = issueGroup.querySelectorAll(
      '.js-navigation-container > div'
    )
    for (const issueRow of issueRows) {
      const lastCol = issueRow.querySelector('div.flex-shrink-0.col-4')

      const span = document.createElement('span')
      span.className = 'ml-2 flex-1 flex-shrink-0'
      const button = document.createElement('a')
      button.className = 'Button Button--secondary Button--medium'
      button.innerHTML = 'Delete'
      const issueLink = issueRow.querySelector('a').href
      button.href = `${issueLink}?github-delete-issues`
      button.target = '_blank'

      span.appendChild(button)
      lastCol.prepend(span)
    }

    // Add delete all button to table header
    const tableHeader = document.querySelector(
      '.table-list-filters > div.table-list-header-toggle'
    )
    const button = document.createElement('button')
    button.className = 'Button Button--secondary Button--small'
    button.innerHTML = 'Delete all'
    button.onclick = () => {
      for (const issueRow of issueRows) {
        const issueLink = issueRow.querySelector('a').href
        window.open(`${issueLink}?github-delete-issues`, '_blank')
        window.focus() // cant seem to work
      }
    }
    tableHeader.prepend(button)
  } else if (location.pathname.endsWith('/discussions')) {
    // Add delete button to each discussion row

    const discussionRows = document.querySelectorAll(
      'ul[aria-labelledby="discussions-list"] > li'
    )

    for (const discussionRow of discussionRows) {
      const lastCol = discussionRow.querySelector(
        'div.pt-2.pl-2.pl-md-0.pr-3.d-flex.flex-shrink-0.flex-items-center'
      )

      const span = document.createElement('span')
      const button = document.createElement('a')
      button.className = 'Button Button--secondary Button--medium'
      button.innerHTML = 'Delete'
      const discussionLink = discussionRow.querySelector('a').href
      button.href = `${discussionLink}?github-delete-discussions`
      button.target = '_blank'

      span.appendChild(button)
      lastCol.prepend(span)
    }
  }
  //
  else if (location.search === '?github-delete-issues') {
    const deleteButton = document.querySelector('details.js-delete-issue')
    if (deleteButton) {
      deleteButton.click()
    }

    await wait(100)

    // not working
    // document.addEventListener('turbo:render', () => {
    //   // on the next turbo navigation triggered by the confirm button below, close the page
    //   window.close()
    // })

    const confirmButton = document.querySelector('button[name="verify_delete"]')
    if (confirmButton) {
      confirmButton.click()
    }

    await wait(1000)
    window.close()
  }
  //
  else if (location.search === '?github-delete-discussions') {
    const deleteButton = document.querySelector('#dialog-show-delete-discussion')
    if (deleteButton) {
      deleteButton.click()
    }

    await wait(100)

    const confirmButton = document.querySelector('button[data-disable-with="Deleting discussion…"]')
    if (confirmButton) {
      confirmButton.click()
    }

    await wait(1000)
    window.close()
  }
})()

function wait(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms))
}