I'm not sure if you are asking the same question as what we are thinking you are meaning ....
IF you are simply squaring the fabric cut edge to the selvage, you are going to do it the same as with other fabrics. Explained well in a previous post.
IF you are asking about squaring the fabric so that the lengthwise and crosswise grains are at right angles, then different story! For regular cottons, you can pull it diagonally to get it squared up. Though the question is always, will it stay there? For a knit .... I don't think you can do that. You just need to live with the knit going on a slant, and go back to how to square it up for a right angle irrespective of the knit angle.
I'm with the others, not so sure that knit fabrics are going to work for curtains, especially when pinch pleated and with as much weight as will be created by the length of the curtains and whatever the width.
However, you have noted you are quite experienced in drapery making, so I am sure you can figure it out, even with it being an experiment as you have mentioned.