So before my fissure, I used to go to restroom, usually after breakfast around 7:30am and sometimes after lunch. On the rare occasion I would go as well after dinner. Since getting the fissure, I have gone like clockwork by 6am just once per day. My pain levels have improved over past month but since pain happens after a BM, I was wondering if anyone had thoughts on how to safely get a new BM schedule to go at night. This way I could hopefully go to sleep and the pain would be gone by morning so I could have a full day.

This would be pretty tough because of the way physiology works. The colon has a wave of peristaltic contraction in the morning as well as after meals. Things get changed up by stress, diet, hormones and other factors, but from the body's standpoint the strongest urge happens in the morning.

maybe you should try sleeping in :)
actually, what about switching time you have fiber/stool softener/etc?