As I wrote earlier, I like to use white glue very much. I prefer it over Titebond. But I figure that the people making that stuff would have added a simple and cheap ingredient such as starch themselves if it really would improve their product. I think I will refrain from doing that...
Starch is used to increase viscosity in gravy. It does leave a kind of gritty feeling at the rear of your tongue. So if you drink white glue, and you don’t mind the gritty feel, then by all means go ahead and add starch.
Amusingly, when they first came out with those little clear packets of laundry soap, and dishwasher detergent, the packets were sticking together. To combat that tendency, the manufacturers added a bit of corn starch to minimize the sticking problem.
Do I want to add to my glue, a product that has demonstrated that it minimizes sticking problems?
In the framing business we used white glue. With small profiles and end grain to end grain joints, miter joint failures were common.
When Corner Weld, a PVA glue arrived, everyone switched, I never heard of anyone switching back.
White glue is for gluing paper and cardboard, or if nothing, absolutely nothing else is available.