if I understand you correctly, you can put all objects you want to reset in a family and add two variables 'Start_X' and 'Start_Y'.
On start of layout you set those variables to the startposition. When you trigger your position reset, you can set the family objects to this coordinates.
+ System: On start of layout
-> Family: Set Start_X to Family.X
-> Family: Set Start_Y to Family.Y
+ Keyboard: On Space pressed
-> Family: Set position to (Family.Start_X, Family.Start_Y)