Understanding Electrical Potential Energy

[iochoa2020]

I am trying to clarify some queries related to the Electrical Potential Energy of 3 point charges:

 

In an empty space without field, when charge Q1 is brought , we stick it on certain position r₁, W=0 (no field, W: Work), U = 0. when charge #2 is brought to position, how it is held in that position?

 

I visualize it that an external force is applied to balance the Electric force, at this point v₂ = 0 (velocity of Q2), if I say a finger provides that external force then when charge #3 is brought close to the system, my finger will feel an extra push due to Q3  charge but Q2 never moves, however, the finger has to apply more force to keep v2 = 0 still work-Q2=0 and Energy change =0. so then I can say that the energy of the ONLY two particle system remains constant, never change even with the presence of the 3er charge?.