When creating a keybind only macro and naming it so it will be inserted at some point in the midst of already existing macros.
Editing the keybind of that new macro right after creating it, will assign the keybind to the macro that was previously in the slot now occupied by the new macro, instead of assigning it to the new macro as it should.

That is, the keybind will be assigned to the macro now moved next to the new macro.
As if the newly inserted macro was actually somehow not taken into account.

Unless blizzard changes their mind, this feature will be deleted in the war within prepatch, so I'm not sure it's worth bothering to fix it 😕

Switching back and forth with another macro, before assigning the keybind, should work as a workaround I think?

Oh that is very, very bad news for me :(

I have found the thread related to it...
I hope they at the very least increase the number of macro per character and the size limit of macros.

Without it, the game is going to turn into a pure PITA for me...

There's no official blue post or anything yet, but here's a link Stanzilla/WoWUIBugs#552

As far as we know, blizzard is still looking into various options, to mitigate problems, but I don't have high hopes of keybind-only macros, or even extended macros, working in next expansion

Thanks, I actually came across that thread indeed looking for related topics on google :)