Is There an Arbitrary Waveform Data Creation Tool for Output on the WE7281 and WE7121 Function Generator Module?

Yes, there is a software called the 707751 Arbitrary Waveform Editor. You can create waveforms using the editor's standard functions or with the mouse. You can read in files created in CSV, or in Yokogawa's proprietary .WVF file format for WE7000 measurement data. Also, the WE7000 Control Software comes standard with a function that converts CSV files to arbitrary waveform data readable by the WE7121.