A first suggestion about the DTMF generator: the future possibility to access and to read an external TXT file, where DTMF codes (1,2,3,4,5,6,7,8,9,0,#,*,a,b,c,d) are recorded as character strings, instead of being obliged to enter them, through the keyboard, in the Audacity interface, and to get the Wav or MP3 corresponding file.
A second suggestion, with the possibility to extract DTMF codes from a sound file (in Wav or MP3 format), and to get the characters corresponding to the codes, with the possibility to save the results in a TXT file.
In few words, the possibility, with Audacity, to encode and decode, DTMF sounds to characters, and characters to DTMF sounds.
As this is very much a niche interest, I think it would be better as a plug-in than a feature that we impose on everyone.
Audacity has a built-in scripting language for writing plug-ins: Missing features - Audacity Support