A few things that can help to make it easier for an elderly person with physical issues or poor balance are:
1) raising up the toilet either with a raised toilet seat, toilevator or getting a taller toilet installed
2) considering if arms on the toilet would help, either a toilet safety frame or a non-wheeled commode over the toilet with arms (using the splash guard instead of a bucket); there are also raised toilet seats with arms but a person has to have fair ability to put equal pressure through both arms or is at risk for popping one side off
3) grab bars beside the toilet
4) pressure mounted floor to ceiling pole beside the toilet
If the actual difficult is urinating or having a bowel movement, there are some suggestions on this page: https://www.caring-for-aging-parents.com/constipation-in-the-elderly.html
Pushing on the bladder area can help with completion of urination.
I have had some clients have increased success with bowel movements by putting a stool under their feet when sitting on the toilet. One version of this is called Squatty Potty.