As the post says let’s take an example. Let’s say I want m/f posts and solo posts, but no solo posts if theres a male.

For your example, at least, "~male/female ~solo female" should work. Of course, that only works because male/female implicates female, so there are no male/female posts that don't also have the female tag.

[Edit: What SnowBoots said is probably a better way to go about it, but this is an alternative]

skinnyjeansowo said:
As the post says let’s take an example. Let’s say I want m/f posts and solo posts, but no solo posts if theres a male.

In general, you can't do that with a single search. For your specific example, you could approximate it by using the "or" ~ search:

~m/f ~female ~intersex ~ambiguous_gender

You can remove ~ambiguous_gender or ~intersex if you don't want those in your results, though ambiguous or intersex characters would still be included if male/female or female is tagged. Of course, if you really don't want, say, intersex characters, you could add -intersex.

This search isn't exactly the same as what you said. For example, it would include female/female posts, which are neither solo nor male/female.