We can do this on isolated cells, but I really don't think we have a way to distribute such a change across the zillions of cells in a human body.
And even if we could, it's not clear how much effect altering the gene after the fact would have. Maybe once your apocrine glands have obeyed the gene and developed a certain way, it's too late.
CRISPR makes gene editing easier, but unless you've got a way to deliver it to every cell, it won't do much unless you're targeting such a small number of cells that it's realistic to have a technician physically inject it into a cell.
That would work for an embryo. Ignoring the plethora of ethical issues and the lack of data on long-term effects, it would probably be pretty easy for a scientist to make the change in an embryo and then go through the normal in-vitro fertilization procedure.
For a whole organism, though, it's more difficult. One obvious solution is a specially modified virus, and that's under research.
There's a lot of stuff here if you want to dive deep:
Whats even crazier is that this video was published 6 years ago and the paper you referenced is 4 years old. With the speed that genetics research is going, both of these are certainly very outdated resources even if the background is mostly the same.
Well, The Thought Emporium made a pill with a virus that modified the genome in at least some of his cells, and made him lactose tolerant for a year and after that he was left significantly more able to handle lactose than before.
So it's absolutely possible to some degree, for some gene manipulation at least.