Maybe I'm being really dumb here.... How can I find the customization (field, custom record, etc) from just a field id? "custrecord_record_change_detail"

The SuiteAdvanced plugin lets you search in the global search bar for it. Thats the easiest way i know. Other than that, you can look at the prefix of the ID to get an idea of at least where to look custom records are always custrecord. Custom record fields are also custrecord though, and those are found under customization > list records fields, other record fields. Other than that you have custbody for transaction body fields custitem for custom item fields custentity for entity fields etc.

Yep, I'm dumb. Records Catalog! Not sure I've ever used it in many, many years.

Oh or records catalog... good call

I've had Flashlight for a few years and relied on it for similar functionality, but it doesn't work that way for this scenario when you don't know the name of the custom record that the field sits under.

Salto is also great for this