Lists. List after list after list.
I have one notebook that they all sit in. The front is one long to do list, probably about 8 pages long now, as I cross off the top and just add on the bottom.
At the back are notes. If someone tells me it's a great sale at the garden centre in two weeks. If DS finally mentions something he wants for birthday /Christmas, it goes there.
As I make appointments, my phone is in my hand, typing it in to the calendar, set up as default to remind me three days, then one day, then one hour before.
Sitting on the sofa watching TV in the evenings, I'm googling on BBC good food what I'm doing for dinner the next couple of nights. Which involves seeing what's in the fridge, then typing two of those things (bacon, mushrooms?) into the good food search bar, picking a recipe I fancy, and screenshot both the shopping list, and the method.
I associate tasks together so the little stuff becomes second nature, if I'm waiting for the kettle to boil, I load or unload the dishwasher. When I microwave something, I unload the tumble dryer. To the extent that if I'm microwaving something, and there's nothing in the dryer, it feels like I'm wasting time.
While the sink is running, give the hob a quick clean. While the bath is running, clean the loo.
I sound like a mad woman, but these, "while waiting three minutes for this, do that" tasks probably add upto no more than half an hour a day, and I can honestly say, my free time is in absolute abundance because of it.
Also, plan ahead. Halloween outfits for DC, get them now. Start on Christmas, make your food shopping lists. Get as ahead as you can, so you can relax at the time.