Does OD have a way to generate DTMF tones?

Yes.

I believe EP supports this notation, an audio tag with the following format:
<audio src="builtin://senddigit/1234" />

Also look in the propertis first page, Enable DTMF tones In prompts. If you enable this it will copy some wav files into your project.

From the online help Enable DTMF tone variables in prompts Check box to enable DTMF generation that copies DTMF audio tones into the project. It will enable "DTMF Tone" when using Phrase Variables in the Prompt Editor.

Look at the sample apps InBandPulseTone and DTMFToneMask

Thanks, samples very helpful. What characters represent sil100, sil1000 and sil500? I figured out by trial an error a space plays sil500, what about the others?