• Open stylus manager page
• F12
• Paste this script in the console

  Or add this snippet. Then Ctrl + Enter

  async function deleteStyle() {
    const deleteBtn = document.querySelector('p.actions > a.delete');
    if (!deleteBtn) {
      return false
    }
    deleteBtn.click();
    await new Promise((resolve) =>
      setTimeout(() => {
        document.querySelector('#message-box-buttons > button:nth-child(1)').click();
        resolve();
      }, 10),
    );
    return true;
  }
  
  async function main() {
    while (deleteStyle()) {
      await new Promise((resolve) => setTimeout(resolve, 100));
    }
  }
  
  main();