Actually it is simpler then you think, if back of the boring bar is all you are concern with you can simply sketch few lines representing specific tool geometry then move that sketch in position on part profile where you suspect potential problem to see the result.
It leaves few things to imagination as far as radial clearance but that part is self explanatory, you cannot fit 1/2" inch bar into 3/8" hole as an example.
We tend to identify boring, threading and grooving bars by size of the round shank as I just did in above sentence but what really matters is "minimum bore", diameter that bar can cut and clear without interference with resulting diameter.
One inch shank boring bar holding 80 degree or 35 degree insert have significantly different minimum bore diameter.
These values are given in tool catalogs but you can simply use calipers to measure distance from tip of the insert to back of the bar shank to get instant estimated value.
I often plot 2D geometry to learn where and how to relieve solid carbide miniature tools to accomplish task and avoid small crashes that ruin parts, to expect CAM system to take on such a task is very trivial and low on list of priorities I would assume.
At this stage you can create custom cutting tips in Fusion and generate G-code to undercut ID profiles axially and radially but modifying tool shanks in arbitrary ways is not part of that functionality.
Fusion
