You can use leather dye and a small brush and drag the grain lines out of the patch across the joint to make it disappear more, You can do this after you have the finish on and put more finish over the dye to lock it in place.
I didn't mention it earlier but I actually blackened the edges of the patch wood and inletted it into the wood very carefully like I would a metal part before I glued it in to minimize the glue line.
This patch didn't have any curl in it so I extended the curl below the patch into the patch with leather dye. All of the bottom molding showing is the patch.
