Item > Transform in the 3D View cannot be moved or merged into SUPERTABs.

Tool in the 3D View:

When added into SUPERTABs, the tool’s Settings Panel in the Properties Editor will not appear.

However, its settings are fully functional and displayed correctly inside SUPERTABs as a replacement.

Image in the UV/Image Editor has the same limitation as Transform in the 3D View — it cannot be moved or merged into SUPERTABs.

Group in the Node Editor:

In Blender 5.0, Group Socket subtabs cannot be merged into SUPERTABs due to API limitations.

In Blender 4.5, Group > Group Socket can be merged into SUPERTABs correctly and fully supported.