javascript:(function(){
  /* Global variables. */
  const gmailResizeSideBarStyle = `
   div.wT {
    min-width: unset;
    max-width: unset;
   }`;
  
  /*********************************************************************************************
                                           MAIN FUNCTION
  *********************************************************************************************/
  function gmailResizeSideBar() {
   if (location.href.toLowerCase().indexOf("mail.google.com") > -1) {
    const target = document.querySelector('.aeN.WR.baA.nH.oy8Mbf'); /* side bar   */
    if (!target) return console.log("Error: Target element not found."); /* error */
    if (document.getElementById('gmail-resizer-handle')) /* no duplicates         */
     return console.log("Resizer already exists.");

    /* 1. reset outer sidebar constraints */
    target.style.minWidth = '100px';
    target.style.maxWidth = '80vw';
    target.style.position = 'relative';
    target.style.flexBasis = 'auto';
    target.style.width = /* close enough but enough to indicate bm ready for use  */
     target.offsetWidth + 75 + 'px';

    /* 2. create the invisible drag handle */
    const handle = document.createElement('div');
    handle.id = 'gmail-resizer-handle';
    Object.assign(handle.style, {
      position: 'absolute',
      right: '-4px',
      top: '0',
      width: '8px',
      height: '100%',
      cursor: 'col-resize',
      zIndex: '9999',
      backgroundColor: 'transparent'
    });
    
    /* add event for resize */
    handle.onmouseenter = () => handle.style.backgroundColor = 'rgba(0,0,0,0.1)';
    handle.onmouseleave = () => handle.style.backgroundColor = 'transparent';

    /* add element to target */
    target.appendChild(handle);

    /* drag Logic */
    let isResizing = false; /* switch */
    let startX, startWidth;

    /* ready resize */
    handle.addEventListener('mousedown', (e) => {
     isResizing = true;
     startX = e.clientX;
     startWidth = target.offsetWidth;
     document.body.style.cursor = 'col-resize';
     document.body.style.userSelect = 'none';
    });

    /* resizing */
    window.addEventListener('mousemove', (e) => {
     if (!isResizing) return;
     const newWidth = startWidth + (e.clientX - startX);
     target.style.width = newWidth + 'px';
     window.dispatchEvent(new Event('resize'));
    });

    /* done resizing */
    window.addEventListener('mouseup', () => {
     isResizing = false;
     document.body.style.cursor = 'default';
     document.body.style.userSelect = 'auto';
    });

    /* ready for use logged */
    console.log("Custom Gmail Sidebar Resizer Active!");

    /* apply min-width and max-width to nested elements              */
    let style = document.createElement("style"); /* new style tag    */
    style.innerText = gmailResizeSideBarStyle; /* global var    */
    document.body.insertAdjacentElement("afterbegin", style); /* add */
   } else {
     /* address is not gmail */
     console.log("Error: gmail not detected");
   }
  }
  gmailResizeSideBar();
})();