Reply To: Blender 2.90: Can surface snapping of extruded bones (CTRL + RMB) be turned off ?

I’ve found it now here in the Blender “2.90 Manual”:

Mouse Clicks

Reference

Mode

Edit Mode

Hotkey

Ctrl-RMB

If at least one bone is selected, Ctrl-RMB-clicking adds a new bone.

About the new bone’s tip:

After you Ctrl-RMB-clicked it becomes the active element in the armature, it appears to be right where you clicked, but (as in mesh editing) it will be on the plane parallel to the view and passing through the 3D cursor.

The position of the root and the parenting of the new bone depends on the active element:

Ctrl-clicking when the active element is a bone.

If the active element is a bone:

• The new bone’s root is placed on the active bone’s tip.

• The new bone is parented and connected to the active bone (check the Outliner in Fig. Ctrl-clicking when the active element is a tip.).

Ctrl-clicking when the active element is a tip.

If the active element is a tip:

• The new bone’s root is placed on the active tip.

• The new bone is parented and connected to the bone owning the active tip (check the Outliner in Fig. Ctrl-clicking when the active element is a tip.).