Keysight Technologies Trueform EDU33210 Serie Guide D'utilisation page 121

SCPI Command
[SOURce[1|2]:]SUM:AMPLitude {<amplitude>|MINimum|MAXimum|DEFault}
Modulating Source
On a two-channel instrument you can modulate one channel with the other.
Modulating source: Internal (default) or Channel#.
Front Panel Operations
Press [Modulate] > Type Sum > Source.
Keysight EDU33210 Series User's Guide 121