Debug Tree Rig
Debug Tree Rig draws a rigged tree so you can check its rig before export: the mesh (see-through), the joints, the skeleton, and a line from each skinned point to the joint it is bound to. It is hidden from the Tab menu. You use it through the Debug folder on Simplify Tree Rig and Skin, which has the same mesh, bonecapture, joints and skeleton toggles.
Reading the bone capture view
Turn on bonecapture and joints. If you see lines running out across the tree, points are bound to the wrong joints and the rig is bad: that tree will deform wrongly in Unreal. Fix it upstream before you export.
See Nanite Troubleshooting for other export problems.
Create Proxy
Create Proxy makes a simple stand-in shape for each piece of geometry, such as a box, a hull or spheres. The assembly nodes use it internally; it is hidden from the Tab menu.
Deflection Effector
Deflection Effector points each growing tip toward the nearest parts of the same tree, so branches can gather or keep apart. Experimental.