@blurfl posted his method of aligning the sprocket to 12 o’clock… I’m summarizing it here:
Use either your chain (or perhaps a spare piece of chain) and drap it over the sprocket. Take a string level and insert a piece of straight, stiff wire through the holes in the level. @blurfl used a section of a clothes hanger. Place the level in between the two sides of the draped chain with the wire poking through the gaps in the chain, as shown below. Use the software to adjust the orientation of the sprocket until the level is… well… level.
You can pick up a small piece chain, either #25 or 25H (heavy duty, but same pitch), relatively cheap to have on hand so you don’t have to fuss with your machine’s chain. If you tend to amazon, I think this is long enough (will know shortly as I’ve ordered it)