How can a bookmarklet be ADDED on mobile Chrome without copying and pasting?
You can add (and execute) bookmarklets entirely in Android Chrome.

The caveat: it takes more work than just drag-and-drop in the desktop counterpart.

Save a bookmarklet (Android Chrome)


Long tap the desired bookmarklet
Select Copy link address
Go to Menu (three dots) and tap the Star (bookmark)
BEFORE IT DISAPPEARS, tap EDIT! (at the bottom)
Erase everything in the URL field, and type javascript:


Side note: If the url of the page is really, really long, you might want to long tap the url contents: the keyboard will appear, and then start typing immediately.

Long tap at the right of the javascript: and then tap PASTE
If you did it right, the begginning of URL should look somewhat like:


  javascript:(function(){lots-of-code-here...
  
  (The : is still in javascript:)

Change the Name to something useful (you'll use it later, see below)
Optional: Pick the destination Folder where you want your bookmarklet stored.
When done, press the back button.
You might want to test the bookmarklet. Read below:


Execute a bookmarklet (Android Chrome)

From How-To Geek (the link you sent):


  In mobile Chrome, you’ll need to launch the bookmarklet from the location [address] bar. Open the web page you want to run the bookmarklet on, tap your location bar, and start searching for the name of the bookmarklet. Tap the bookmarklet’s name to run it on the current page.