You can bud-graft into the trunk or maybe even side-graft a small twig. You can notch above an existing bud to encourage bud growth, and graft to the resulting branch. You cannot just stick an entire branch into the trunk (if that's what you are proposing) and expect it to grow.

its an apple tree.. it has dormant buds.. cut the top off.. and a hundred dormant buds will pop from below the cut ...

i really dont understand the root of the issue ...

if you want a production tree.. you have to obliterate its height.. and frankly.. make yourself one ugly backyard tree ... its a real quandry for most homeowners .. orchard trees are plain ugly ...

there is a fruit forum.. should you wish a diversity of opinion..

and a picture sure might help clarify the situation ...

i prune trees up.. for my safety.. the thought of grafting low.. to do the opposite.. really confuses me.. lol ..

ken