3-in-1 or Interchange Jacket

Oh yes, these are very handy. I do find with the Columbia ones that the zip in jacket is not quite as nice a quality as one of their regular jackets. Slightly thinner for the ones I've seen/had. You can also cobble these together on your own with a roomy sized waterproof rain shell and a puffy vest/jacket or polarfleece vest/jacket. You don't have the interior zippers to keep them together but not a huge problem.

Since you are in the Seattle area you can probably try on some in other brands at REI. I don't think they carry this particular brand but another outdoor store in your area might.

I live in a cold weather environment. Used to ski with my favorite 3 in 1. The only problem I see with this is to stay really warm it's nice to have a coat that comes a bit lower - at least below your bum so when you sit on a cold bench your coat is under you. If you want to stay truly warm a knee length or maxi length coat is best. I've had a few 3 in 1 jackets and really have only taken them apart a few times. I'm going to the christmas markets with my maxi down coat from lands end. Last Christmas market trip I wore a knee length down which is really my go to in the winter.

If you really want a 3 in 1 I'm pretty sure they had a lands end version at Costco last time I was there. Land end was having a great sale yesterday which included these coats, but not sure if it's still going on.

I am several years younger than you and know about them, but I personally can't stand them. I just don't like bulky anything though, and prefer to go with thinner layers.

We did the Christmas Markets in Munich and Salzburg 2 years ago and I just took a thigh length down jacket. I didn't even bother taking my rain jacket. I was plenty warm with gloves and a scarf. I run hot though.

This type of jacket is very common. What's nice about the one you picked on Amazon is that it looks like a nice coat, not a sporty ski jacket. I'm not familiar with that brand, though, so who knows? My one beef with it is that the puffer doesn't have a hood. I have WAY too many jackets with no hood, which I feel like I need here (I also live in Bellingham).
I would take a look at Sierra, the Columbia outlet in Marysville, Backcountry Essentials here in town, of course REI (which now has a discounted "used" section in the Sehome store that's not to be missed--some of the stuff is "worn once" and nothing wrong with it), as well as Costco. Of course, as another commenter suggested, you can simply layer two jackets (maybe two you already have?).
A hot tip for traveling with any puffer jacket is to use it as a pillow when you're not wearing it. I have used the little bag that sometimes comes with a set of sheets and is made from the same fabric (I had some that closed with a drawstring, but the ones I have now are velcro--yuk).

The downfall with these is they can be very bulky. I ordered and returned so many coats for that reason. For our Christmas market trip last year, I brought this jacket and wore it constantly. It’s not bulky at all. I loved the longer length. I brought a waterproof raincoat that I could wear over it, but never needed it. https://a.co/d/gCx4GC9

On the plane, I folded it up and put it in a zippered travel size pillowcase and used it as a pillow. Worked beautifully.

This is what I have, in deep blue. It is truly waterproof (PNW or anywhere!) and the hood is great (I hate umbrellas). It is expensive but really high quality.
https://www.fjallraven.com/us/en-us/women/jackets/shell-jackets/visby-3-in-1-jacket-w/?v=F84131::7323450801700
It's not at all bulky, I'm only 5'2" and petite and longer down styles can look like a sleeping bag on me. You can't tell there's a zipped in lining at all. I wore it in Montreal (freezing cold and icy snow for a week) last winter and stayed warm, despite usually always being cold. (I wore a wool turtleneck w a silk long underwear top beneath.)
I wore it on the plane so it didn't impact my carryon limit.

I have a North Face model and it is not at all bulky. The inner jacket is a light puffer, and their rain jackets are excellent quality.

Cerastez, I am a guy much too smart to get involved in women's fashion discussions.

For practical planning, if your Christmas Markets are in Central Europe then the temps after sunrise can be 30 to 50F. Cold does not begin until January. So be flexible (layers). You will be inside a lot, maybe having to carry the coat in a museum or a tour of the Opera House. The restaurant for lunch or dinner will be uncomfortably warm in a heavy sweater. You have to get in and out of the taxi.