Find it here:
MOUS_ICO Menu: Noise > Calculation point > Edit
or
MOUS_ICO Menu: Noise > Calculation point > Dialog box
MOUS_ICO Select exactly one point in the list
MOUS_ICO Dialog box: Change
or
nco: Select a calculation point
MOUS_ICO Popup menu: Change
For a description of the functionality, see New.