@roseee
I can certainly tell you what my routine is with laxatives. Here is what Mayo Clinic has as an overview. There is a nice chart explaining how each works.
https://www.mayoclinic.org/diseases-conditions/constipation/in-depth/laxatives/art-20045906
I eat fiber-rich foods, lots of whole grains. I drink a consistent amount of water. I also exercise regularly. I use olive oil on quite a bit of my food that works as a laxative. Maybe try adding some/more EVOO (extra virgin olive oil) at meals and splitting your MiraLAX and taking it throughout the day.

As far as medications I use MiraLAX, senna (and senna tea) and prescription lubiprostone. They are each split and taken at different times which seems to help keep my system working consistently. Based on my experience I would recommend having a conversation with your GI doctor about coming up with a plan to make changes one at at time based on that makes sense with what they think is happening with you. You know your body and they know the science. Together you’ll make the best decisions.

I am interested to hear what you find out about getting an appointment at Mayo Clinic. Will you come back and provide updates? Do you think you will make MiraLAX changes, or maybe talk to your doctor?