I took a quick look at the documentation for the 2120 and did not see a similar setting. You might wish to visit the GS forum and submit a query on the matter and perhaps they can advise further on how to do, if available, or perhaps include in a future firmware release. In the meantime, you could explore "parking" and its available options. Take a look at the settings and you will see some options on how it works.
The 1450 model has a call waiting tone enable and disable which I did not see in the 2120. Sometimes, the manufacturers will use essentially the same methodology for the two (call waiting/hold functions with regards to tones) but I could not really tell if that was the case.