If you want to weld multiple subtools together to create one seamless mesh, here’s how…
Supposing that you have two subtools in the Subtool palette.
Turn on Live Boolean (click the Live Boolean button to activate Live Boolean).
Then navigate to Subtool > Boolean and click Make Boolean Mesh.
This will scan through all the subtools in the Subtool pallet, weld them together, and create a new Tool that can now be found in the Tool palette.
This is different than merging subtools in the Subtool palette (using Subtool > Merge > MergeDown, for example). That technique combined the subtools, but does not literally weld the geometry together.