My question refers to a deck wherein I want to place the wooden surface boards on a 45-degree angle and then trim the object down to a square.

I have a deck outlined as neatly as possible to the shape I want, but the edges are like saw teeth, which is what I want to trim off.

Further, is there an allowance to group a bunch of objects together to become one object?

Often times when trying to moving objects and I try to grab them all, I will sometimes drag the footings under the object as well, which I don't want.

I use Inkscape regularly, and it is a feature which allows me to do these things when I am creating drawings in that program.