I believe the dialler UI is closed, BICBW. I'm not sure we're at that point. People who've wanted to develop something to scratch their own itch have either created patches already or are now working on them to get them shipped. There's no "oooh, what should we work on next?" going on. However, non-technical people can contribute by approaching developers (such as #11832 - offline IMAP support) and asking for them to contribute to the CSSU effort.