Moving the buttons on your button boots (or button shoes) was a perfectly normal part of the fitting process with new footwear. The good news is that it's easy to get the perfect historically accurate "snug" fit, though it does take a little time.
Fold the fly (flap) over your leg, pulling it tight.
Cut all the buttons that need to be moved off the boots, snipping the thread holding them in place.
With a pencil, mark the new placement of the button through the keyhole end of the buttonhole. You want your boots to be *tight.*
Take the boot off.
Poke two small holes right next to each other (using the seam ripper) on either side of each new button pencil mark.
Stitch each button on, passing through the button's looped shank and the two holes in the leather several times. Beeswax will help keep your thread from tangling and form a nice tight loop and knot.
Tie the thread off however you like.
Repeat for each button.
Repeat for the other boot.
To get your boots really nice and tight, stitch your buttons 1/8 to 1/4 inch further than the mark you made with the pencil. The leather stretches and eases with wear, and you want the boots to fit tight all the way up, like a corset for the ankle.