How to change the CSS file for the TinyMCE (version 6) on the fly without hard reinitializing?

Question

TinyMCE is often used in the CMS Software. The CSS file, that is currently bound to the TinyMCE editor, needs often to be exchanged.

There are two important things:

• The current CSS file must be cleanly unloaded, otherwise their CSS rules will still affect the contents of the editor.
• If the CSS file has been just changed but its name remains the same, reloading might have no effect because of cache.

Here is the solution:

function reloadCSS()
{
  // remove all previous CSS files
  tinymce.activeEditor.dom.styleSheetLoader.unloadAll(tinymce.activeEditor.contentCSS);
  
  // clean up the variable for storing the list of CSS files
  tinymce.activeEditor.contentCSS = [];

  // add the timestamp to the css to force loading from the server (not from cache)
  let new_css = 'editor.css?t=' + Date.now();

  // add new CSS files to the variable for storing the list of CSS files
  tinymce.activeEditor.contentCSS.push(new_css);
  
  // load new CSS file into the editor
  tinymce.activeEditor.dom.styleSheetLoader.load(new_css);
}

I tried to do this first with hard reinitializing but it was not so effective.