@NeverDie , you got it right, mine has the advantage of being self holding, which is quite an advantage if you want to debug, I tried, to debug in the past using the keyboard with only one hand, not very efficient
As you can see, the one in the left side, is holding by itself, it does not has the cables soldered though, the one on the right is my first iteration, but the side holders are weak and broke with time.
It is true that the fact of picking the two side points, it makes it self aligning.
The blue versions are the newer ones, where you can slide it in with the pogo pins stretched out, and then you press it in and lock the open space in the bottom with that small blue little thingie that we see unused and free in the middle version. So no rubber band required, all is static mechanics.
Both middle and left versions are available, the middle version requires glue to fix the pogo pins in the printed shell after being inserted the first time but makes soldering the wires on top easier. The left one has a roof holding the pogo pins but they're harder to access for soldering the debug wires in them and also printing is with slightly more debris given the complex bridging.
One way or the other, this managed to get me a self-standing pogo pin adapter of an already existing board. Indeed if you design your own, you can think of those you linked, but if you're short of space, you can also fallback on such custom 3d printed solutions.
This nRF52840 usb dongle is an amazingly powerful board and so cheap, that I'm confused why Nordic did not made the debug for it simpler, feels like they prefer to sell the dev kit for prototyping, but they don't know how hobbyist like to prototype on the final cheap product. I could afford 5 of them to experiment with some mesh protocols.
So if you have access to 3d printing and would like to give it a try, I'll stay around and help if needed, also if you have improvement suggestions, I struggle with fusion360 till I get things done.