Merge the 3d model using the standard 3Ds Max menu.
Holding down the SHIFT key while dragging the model from Project Manager into the viewport will summon the standard 3ds Max menu, which we usually see when dragging the model from Windows Explorer.
This video for the tutorial about merging 3D Models to 3Ds Max using Project Manager
https://bit.ly/2XXhzGr
Product page:
https://bit.ly/2KsE3XS