Any way to add POIs on a really, really long tour made in a different route builder

Use Basecamp to add the POIs?  That works for other Edge units so should work for the 1040.

Would that mean I'd have to import the 32 routes into Basecamp, or can I highlight some POIs in Basecamp that will actually show up when I ride the routes made in Komoot?

My point is that I want to have my routes imported from Komoot into the 1040 in as few steps as possible, but still have some way to find POIs. I'm assuming the POIs unfortunately must be listed in the actual route GPX file to show.

A way to manage POI's on the edge 1040 would be much appreciated in general. Especially creating your own is a pain. On my Fenix device, it's a breeze using Garmin explore application ... works great. Actually off topic but it's insane how well creating a course using the Garmin explore works vs Garmin connect app on your phone.

POIs are nothing to do with routes.  They are just saved locations.  By POIs are you meaning course points which can be embedded in routes?  Course points in routes won't show up in the POI list.

On the website Garmin route builder, I can make a route, and manually create interesting waypoint with an array of categories, like Checkpoint, Gas station, Cafe or whatever. Once synched to the 1040, I can use that route to navigate by, and I get a screen that lists my custom waypoints with distance and ETA.

Those are course points, not POIs.  They are embedded in the route file and can't be accessed outside of the route.  They have to be added in whatever tool creates the route file.  I don't know if you can add them in Komoot as I don't use it.  RidewithGPS can add them.  The Garmin route creator can as well as you have found.  I would investigate whether they can be added in Komoot.

I am not familiar with Kamoot but would imagine it must also support "Course Points" (sometimes also called Cue or Cuesheet entries). Once added to the course these will show on the course map, will display at the bottom of the screen as you roll over the position, will be listed in the Course Point screen (called the Up Ahead screen in the 1040?), the list includes a short name and the distance to the point from your current location, also there is a data field (Crs. Pt. Dist.) which displays the distance to the next course point.

PS Only .FIT & .TCX format routes support "course points" not GPX

There is a way to click on different waypoints in Komoot, and have them be a part of the route as waypoints with their actual names (as opposed to "Waypoint 1, 2, 3, etc).

I can't find a way to export as TCX from Komoot, but tried making a route in Komoot, adding a couple of stores, bus stops, etc. When exported as GPX, then imported into the Garmin Connect map, they do show up in the route, but just as small dots.

When I import it via the Komoot app to the Garmin 1040, the waypoints are nowhere to be seen :-/

The same applies if I send the route from Garmin Connect to the device: No waypoints present.

That's why I wrote about the lack of a TCX export function on Komoot (even premium subscription).

(However, when exporting as GPX, my waypoints are actually shown as small dots on the Garmin Connect map, so there is *some* info about those waypoints in the GPX, it just doesn't show on the 1040.)

I sent feedback to Komoot about adding TCX export as a feature, now that you guys made me aware of it.