Tektronix TDS2000C series User Manual page 130

Reference
106
Remove Waveform. To remove a waveform from the display, push a channel
menu front panel button. For example, push the 1 (channel 1 menu) button to
display or remove the channel 1 waveform.
NOTE.
You do not have to display a channel waveform to use it as a trigger
source or for math operations.
NOTE.
You must display a channel waveform to take measurements from it, use
cursors on it, or to save it as a Reference waveform or to a file.
TDS2000C and TDS1000C-EDU Series Oscilloscope User Manual