Don’t set them in concrete, bolt them onto a concrete pad, this way you can build all the structure up and bolt them down when you are happy.
too many things get drawn up with little thought as to how to build it.
or you need two wooden posts and a string line.
or the alternative method is to dig your holes and build the entire structure, but don’t concrete the posts, just hang them in thin air by putting temporary blocks under the structure.
when you are happy it’s all correct get a load of concrete at once and concrete in all the posts at the same time.