What specific issues or topics are most important to American progressives (liberals)?

I'm not sure I would be thought to qualify, but I'll answer anyway.

1. health care
2. wage/programs and benefits for poverty and/or a little above or seniors and/or those with disabilities.
3. justice reform for minorities.
4. get out of most of wars we are currently in, but most importantly, stop supporting the Saudis war in Yemen
5. support for Palestine independence from Israel and a state of their own or at least equal rights if it ends up being one state. (doubtful)

Justice reform for everyone.

Most liberals want to violate people's civil rights for fun by banning pistol grips on rifles.

I don't know if it is their number one issue, but it's up there near the top of the list.