Thank you oneeye for your encouragement. A the age of 70 something - I am so looking forward to 'Spade work'!
Got you, I turned 80 last September, and I don't go for digging too much.
Firstly my compost heap, it's made out of quartered four foot logs and takes everything, leaves, sticks, the lot. About once a year I go through it with the fork and anything not rotted down starts the next heap, the rotted stuff gets spread on the surface, at most I turn it lightly with the fork to mix in a bit of soil, after that I rely on the hoe. It will work its way into the soil fine without digging, where the heap has been will be lovely, full of micro life.
I take that spreading on the surface further, a 'horsey lady' down the road lets me dig out her old heap of horse manure, and that is treated the same way as the compost, and I actually spread a bit on the compost heap as well to help things along.
About the only time I do spade work is starting a new bed, when I take out the top soil and put wood down before putting it back. How long that will last depends on the wood, but it is going to be a matter of years at least before it needs digging of any sort. The disadvantage with compost heaps is anything within about eight foot is going to get 'slugged' to some degree, but that's not an initial problem usually.
In the OP you talk about 'difficult shape' and 'vertical gardening', does this mean you are on a hillside? That can be a real plus, a log wall and infill behind it to make it terraced, and voila, a nice little bed that won't need digging. It's amazing how quickly you can fill a space like that if everything goes in, wood at the bottom, then all the sweepings, emptied pots, spare bits of compost, anything and everything that would have gone in the bin, or a garden bin. If it is stuff like leaves, or green waste, I run the lawn mower over it first, and I try and mix lawn mowings in a bit so they don't make one solid block.
The other thing do is 'little by little', If there is something that is a fairly heavy job that would have taken me most of the day when I was thirty I'll spin it out over a week, or maybe two, and then do less demanding stuff , like planting seed or clearing up the greenhouse, for the rest of the day. There is always something, raking leaves out of corners, walking behind the mower, weeding a row, hoeing a patch, painting a fence, and in between, just a little bit of digging if I have to.