So, let's say I have an Action available to me, and I also have a Bonus Action, AND I have Extra Attack. Does that Extra Attack hold "within itself " the ability to use one more Bonus Action?

Extra attack -- You can attack twice, instead of once, whenever you take the Attack action on your turn.

So there's no additional Bonus Action.  If you use your Action to take the Attack action then you substitute two attacks (or more) in place of the attack that you get from the Attack action.

Cool! Thanx! 😀 

And also, if you are a fighter and use Action Surge, you get another action (that you can use to attack with extra attack) but you do not get another bonus action. 

Ah yes, Action Surge. Thanx, I had forgotten about that one. 😀

Quote from pafender >>

So, let's say I have an Action available to me, and I also have a Bonus Action, AND I have Extra Attack. Does that Extra Attack hold "within itself " the ability to use one more Bonus Action?

 The Extra Attack feature is only usable when you use the Attack action.

You don't have a bonus action to take unless you have a feature or effect letting you do so, which may tells you in which circumstances it's usable. There's no feature letting you use more than one bonus action on your turn.

Like ThriKreenWarrior said, Action Surge doesn't give you an extra bonus action to take there is an official ruling in Sage Advice Compendium on this subject ;

Does the fighter’s Action Surge feature let you take an extra bonus action, in addition to an extra action? Action Surge gives you an extra action, not an extra bonus action. (Recent printings of the Player’s Handbook no longer include the wording that provoked this question.)

What's funny is that I recently gained access to additional sources and saw that in Sage Advice after I had posted my question. 😀🤣🤪