I would like to constrain two bodies by their construction elements, like symetric datum plane, axis, datum point. I cant make datum plane in assemle which would be constrain to part, and when i make plane in part it is not visible in assembly.
you can make datum plane,axis,line by using point in assembly.
Answered with a tutorial: https://grabcad.com/tutorials/how-to-make-datum-plane-in-assembly
It's possible to make datum plane in an assembly and then use assembly constraints to constraint the parts with the datum plane of the assembly.
Using "center" constraint and option "2 to 1" you can symmetrically position these two bodies according to the datum plane. Moving one part will move the other part/body too then.
Moving the datum plane afterwards will affect the position of the parts constrained to it, as designed.
Set your datum plane in the parts, not the assembly.
In your assembly navigator right click the part you want to constrain -----> Replace Reference Set----->Entire Part and all planes etc apear and you can constrain the components as usual.
Don't forget to go back ---->Replace Reference Set----->Model when you are finished constraining or else the Datum Planes etc apear on your drafting page