We are commanded to keep Holy the Lord's Day.  If it can wait til Monday, then wait.  If it's something important, then bid.  If it's something super quick, then bid.  
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If it takes a lot of time on a Sunday, but it's important, then do it once, but only once.  Next time, plan ahead.  
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The point is, Sundays are for God.  They are not for work, tasks, small jobs, normal stuff.  Sundays should be DIFFERENT from every other day (more God/religion focused).  Every now and then, an exception comes up where "normal things have to be done" on a Sunday, but you should plan and work to make exceptions very rare.  This shows respect for God and His day.

I don't know.

You could click-click order a car on Sunday -- would that really damn you to hell for all Eternity -- such an action is incompatible with Charity/the Love of God/Sanctifying Grace?

I would question if that is even a venial sin.

Remember, the Orthodox Jєωs were commanded not to even light a fire on the Sabbath. But today, they foolishly extend that to one's OVEN starting a fire. So there's a special "Sabbath Mode" where the oven is kept on, so you can adjust the temp up/down during the Sabbath, but you didn't "start a fire". Pharisaical, I know.

Is swiping and tapping on your phone really a sin? You can swipe and tap countless other things which aren't a sin.

I just think online commerce is SO easy, and doesn't require YOU or OTHERS to do any work, so it has nothing to do with "shopping" or "making others work" on Sunday. The only thing it has in common -- money is deducted from your funds, and you become set to acquire some merchandise in the near future. Seems pretty fundamental, I know -- but acquiring merchandise isn't a sin -- you can give or be gifted things on Sunday, right?  And if you can't reduce your bank balance on Sunday, then you can't donate money to the collection at Church.

From the time I decide I need something, it takes about 5 minutes to browse the options, pick one that isn't too cheap but not too expensive, has 4-5 star reviews, and click-click order it. 5 minutes is not going to put a dent in my day or take away time or attention from things spiritual.

The important question is, WHY is shopping traditionally excluded from lawful actions on Sunday? The time it takes up, the ongoing distraction from spiritual matters and attention we ought to give God at least once a week, and the fact that it causes others to put in hours at work, and possibly miss Mass and certainly stay too busy to attend to their own souls and spiritual matters.

But "one-click ordering" does none of these things. So then?

The problem is, online ordering didn't exist before Vatican II. So we Trads are left to our own devices, basically applying principles of moral theology to new situations. We are "on our own", like the Jєωs in Judges 17:6: "In those days there was no king in Israel, but every one did that which seemed right to himself."

No, it's not. It's only public commerce such as buying something in a store on Sunday that's forbidden. Buying something online is simply a communication to another computer to send you something. It would be like a hundred years ago if you wanted to order something from the Sears Catalog and put an envelope with a check and an order form into a mailbox on Sunday. That would not be a sin either.

I believe it was Saint Bernadette who told one of her family members to stop selling religious goods to pilgrims to Lourdes on Sundays and Holy Days because it displeased the Lord and Our Lady. Makes me wonder about book stores in Churches.

 I've never seen anyone work hard in a church bookstore.

Did you even read what I said before laughing? St. Bernadette's relative was not working hard selling medals and prayer cards to the Lourdes pilgrims either. The act of selling itself was the sin, not the working.

And Jesus went into the temple of God, and cast out all them that sold and bought in the temple, and overthrew the tables of the money changers, and the chairs of them that sold doves

Just to look at it from a slightly different angle, online commerce could actually be a tool to enable us to avoid servile work, and to avoid physical commerce (going into stores that have to have people hired to staff them, stock the shelves, clean up, and so on).  Seen that way, it could allow us to stay at home, stay with our families, not have to be out in the world of work, and so on.

Seen that way, the only problem I can see --- and it is a considerable problem --- is that once you click and place the order, that sets into motion a chain of events which requires people to work immediately --- the Amazon warehouses are a case in point.  Just because we can't see the person who is working, doesn't mean that they're not being forced to disregard the Lord's Day by putting in their own servile labor.  (But a lot of people work at those warehouses out of necessity, the pay is fairly decent, and there may be few if any other jobs in that community that are as easily accessible.  Frequently, in the world or work, you do what you have to, not what you'd prefer to.)

As a rule --- and I shall not dogmatize on this --- I do not engage in any online commerce from Saturday evening to Monday morning, unless it is something that has to be ordered and set into motion, to arrive as quickly as possible, such as necessary things for our home where I am caring for disabled parents, including a father who is gravely ill.  It is the same as if he needed dietary supplements from Walmart on a Sunday.  I do try to plan so as to avoid such shopping, but in circuмstances such as this, that's not always possible.  Things come up.  But if it's some widget that I don't have to have in a short time frame, then I hold off until Monday morning.  That's the best way I know to deal with the conundrum of "is online commerce something that is forbidden on Sundays?".

Matto, how about buying meals on Sundays so that my wife doesn't have to cook?

I would say that is probably fine, or at worst venial. I don't know all the details as I was never properly taught. All I am going by is a few quotes from Saints saying it is a sin to buy and sell on Holy Days unless necessary, the Cure of Ars and St. Bernadette, with no explanation, and I just looked at the Catechism of Trent that says you should not conduct "Business" on such days without a full explanation. What I do on holy days is not buy and sell, except for food and drink. So I think going to the restaurant so your wife doesn't have to cook is fine, and I live as if it were fine, but I don't know all the details. And about the Church bookstore, I hope it is okay as the priests should know better than me, but I sometimes think about St. Bernadette.