I'm sorry if this has been addressed before or has been fixed in the latest beta.

in Spine 3.6.50, if the parent bone has a different icon from the default, all the child bones will have the same icon in the tree regarding if they're bones with a length or not. (When creating them as you go, not changing afterward)

Visual:
https://gyazo.com/76c90f806eb0c6b40b581d1f0988aff3

L_Arm I've manually changed and changed the bone lengths after creating
R_Arm you can see all the icons being the same as the parent bone in which I created them
(You can also see the pink bone Axe_Base (in bottom left) having a different icon rather than a bone icon when it has a length)

Reproduction steps:

create a bone, change the icon (different from default), create child bones with a length, look at the icon in the tree.
(in case that doesn't work, my root has a different icon from default too)

_

The cool thing I like is that the child takes over the parent's icon (and name) when it has no length, but it should have a bone icon when it has a bone length, just like it does/behaves with the defaults. I use the icons a lot for visual organization