The seeds of this so called tree spinach distribute all over the place. When the plants start to grow I thin them out and, depending from what I am cooking, I use the little plants in salad, stews, soups and when I don't use them right away, I dehydrate them and afterwards put them in my blender to cut them into small pieces. Once done I mainly use the dried parts together with other dehydrated greens in soups or stews.
When I pick them, I choose those that are a bit bigger and I go through my garden beds once a week to harvest.
Lamb's quarters is a close relative to magenta spreen.
Time ago I found a video where someone was substituting part of the wheat flour with magenta spreen flour and made bread ... not sure if I like this, because the green bred looked a bit weird.
Be aware: once you have it in your garden and let it go to seeds, you won't be able to get rid of it again. The seeds survive in the soil more than one year and come up spontaneously, when they feel like doing it.