Sometimes phonologies have symbols that I haven't seen in the IPA, such as
k͜xʰ. Wondering how I go about finding out what these mean, and/or why they don't use the IPA symbols. Wondering if this means the IPA is missing some stuff so they had to use something custom.
k͜xʰ is completely standard IPA, you just have to note the other parts of the chart that indicate diacritics like ʰ, ʲ and the use of the tie bar. Other superscripted letters such as raised vowels or fricativesare outside of sanctioned IPA practice. They are used because they denote the same kind of fact that writing [pʰ, pʲ] denoted: there is a sequence of articulations, p plus h or j, which are phonologically unitary – they are a single segment. IPA allows the encoding of that segmental unitariness in some cases, and raised vowels and fricatives extend the logic of raised-letter diacritics, without official sanction.