Slur point-alignments

More important are the extreme points, but it might as well apply to all of the points. The concern is if a composer or transcriber wants a default leveling of the extreme points under certain circumstances, or wants to follow a particular pattern for slurs, it has to be done by eye-balling the positions rather than having available numerically-precise editing. The question then is what would h:0.0/v:0.0 be equal to for a point? It seems the default positions would have to be independent of note placement for this to be most useful.
 
The initial idea was for an "horizontal" checkbox on a slur to force equal vertical placement of the extreme points, just like I think this should be available to the tuple-brackets -- like the inversion of "allow diagonal" for lines and (de)crescendos. From this idea stemmed the notion of numerical editing of the points. I understand that it isn't "standard-convention" to use equally-leveled slurs or brackets, but I've seen scores that use this very tastefully and it wouldn't hurt to have a better means to easily attain the leveling of some objects: namely slurs and brackets. To get right down to it, this is all stemming from a desire to have a more systematic approach in positioning these elements, but of course, sticking to "eyes only" and the "hands-on mouse" treatment will work if that's the only option.