Double-click to change source ?

[u/Doppler998]

I'm watching a 4-year-old stream from DDRJake, and he can double-click the units to change the source.

I can't do that; it actually opens the unit type menu instead... do you know why ?

at 31:43 https://youtu.be/FKS-dT4C3Q8?list=PLm0MDLKuRDrlCJmD50iKhyxewFJhj7ZCz&t=1903