@Kent1Cooper wrote:
Under what starting criteria? ....
The reason I ask is that what you're starting with would have a huge effect on how the bullnosing would be accomplished.
You might, for example, have something with side Lines already drawn [such as at the full depth of parking spaces], and you want the Arc drawn to connect the ends but you also want the Lines shortened so that the extent of the Arc bulge matches the extent in that direction of the original Lines [i.e. the depth of the parking spaces]:

That could be accomplished with a modification of the CapEnd code [and presumably at the same time a reduction of it to only the Arc mode, eliminating its other options].
Or you might have something like a Polyline with a squared-off end that you want rounded at the same extent:

which would require an entirely different approach [change vertex locations and the bulge factor for that segment].
Kent Cooper, AIA