colder and cnewer

[bruno-]

q is pretty saturated, but alt key maps are still free.

nnoremap <silent> [<Esc>q :colder<CR>
nnoremap <silent> ]<Esc>q :cnewer<CR>

No issues as in vim-rsi link1 link2.

[ipsquiggle]

I've just been using [c and ]c for this. I didn't see that anything else had taken this mapping, and I definitely use this one about as much as ]q and ]f (my most-used unimpaired commands) so it makes sense to me to have it on the simplest sequence possible.

(I'd also say these are a candidate for including in unimpaired, at least in some form. Is this where I suggest such a thing, or should I just make a PR, or...?)

[adambyrtek]

[c and ]c are used by Vim for navigating between diff changes (see :help ]c) and by several plugins (like Signify and git-gutter) for navigating between chunks, so it wouldn't be a good idea to override them.

[tpope]

One thought I recently had is that we could remap [f in the ]f in the quickfix window only.