Formatting a whole note hairpin decrescendo with specified ending dynamic

Click on the hairpin to select it, then adjust the position of the right "handle" (the little box) to change the width of the hairpin. Be aware that every time you change layout in that portion of the score, this will/may re-adjust itself. So simply ignore it until the very end. That is, once the score is complete and you're not going to be making any further changes to it, then make this adjustment ... and until then, just ignore it.

Another way to deal with it, if your ending dynamic is "niente" is to use the hairpin with the "niente" circle.

(Those two images are supposed to fit side by side rather than one atop the other.)

Be aware as well, that none of the niente marks actually affect playback as they ought :-(

In 4.4 (out soon!) there's a feature to accommodate precisely this requirement:

• Apply a hairpin to the whole note
• put the n on the end, either by applying it to the following note/rest, or directly to the hairpin itself (which has the same result, i.e. puts it on the following note/rest)
• press Shift+Alt+left to shunt the n back to the end of the previous duration. This is a special position which will keep the correct layout even when the score reformats.