Revit does not do this well. Check out using a Curtain Wall instead - with or without a baluster post.
20170713-CurtainWallAsRailing.JPG

I'll second what anthonyB suggests. Too much effort required to achieve what you need with handrails.

Revit Curtain Walls will get you there, provided your posts and rails are extremely simple (just extrusions or profiles). The moment they get any more complicated than that, the curtain wall tool will fall on its face for making railings. Also, the moment the panel is anything more than one monolithic material, youll need to use a family regardless (either a curtain panel family or a baluster family). Both have ups and downs there.

But there isnt a fast way to "trim."

When i do custom rails in Revit, i make "each length" of the Rail its own Revit Railing, that way they can all have different "types" of Baluster Panels, which can have different lengths. So i might have one side ofa landing using the 33.625" panels, and the next side of the landing might use 34.25" panels.

It might sound tedious, but thats generally what we are *drawing* anyway. I rarely see all panels the same size, and then one odd one cut off at the end. Most of the time i see them evenly spaced down each run.

The attachments called LinedUp and Balusters, are all Revit Railings. Similar to the limitation (line of demarkation (for me)) of Curtain Walls being custom baluster shapes, the limit of Revit Railing and Baluster Panels is when the SHAPE of the Baluster Panel itself needs to change. They can be flat, or then can be sloped. But if they need to do BOTH, you need something other than Balusters.

In that case (attachments CMS2 and CMS4) i used Balusters for the mounting structure, and the panels themselves are just walls with edited profiles. Using walls and then using a Revit Railing for the Rails and Bars, works great too.

the result is prefect, using curtain wall instead of railing

Thanks all of you

another railing in my project, the panels are not even at all.
Lucky, my boss do not have any design output right now.

To Twiceroadsfool
Your railing looks cool and excellent
In attachments CMS2 and CMS4, you used the railing to build the railing's post and used the curtain wall (Profile edited) to build the attached glazed panel, is that right?