Allow macros to write/prefill text to picker prompt

[jnns]

I'd like to create a keybinding that opens up a symbol picker that narrows the selections to only show functions: %k f for example.

While the search picker allows prefilling using the search register /, there's no prefilling for the other pickers.

If I create macro that's supposed to write into the picker prompt, characters following the picker invocation are disregarded:

[keys.normal.space.space]
f = "@<space>s%k f"

Is there a way to accomplish what I'm looking for already, or is it feasible to allow macros to write into the picker prompt?

[John-Toohey]

I would really like this feature also: when refactoring code, I often want to record a macro of <space>D%se e<ret> to go to the next error in the project; but I don't think this is currently possible, :(.