If you have 1-D array of XY-clusters and you want to extract all the X or Y values as a 1-D array just wire the cluster array to a for-loop with auto-indexing on, then wire the cluster element inside the loop to an unbundle function, and wire the element you want an array of out of the loop with auto-indexing on...the array you get from the loop can be given to the write to spreadsheet function.
If you really want to write both the X and Y values the method is the same only you join the two values inside the for-loop to a row or column of the 2D array using the build array function, or have a 2D array predefined in a shift register and use the replace array element function. The write to spreadsheet function will then accept the 2D array. You need to make sure both the X and Y values are of the same type to get them into the same array though, if they are not - convert them using the convert functions from the numeric palette. I assume you are aware that there are waveform file IO functions as well so unless you need to save the data as text for other reasons you could feed the waveform to those instead.
