I have income parent categories of Employment, Investment and Other. I would like to move the built-in income categories, like "_RlzdGain" under my "Investment Income" parent category.
Those "underscore" categories are special, and internal to Q. I doubt that this request will ever be implemented as it would require significant coding change by Q to know where those "special" categories would be found.
Also note that those categories should NEVER be directly used by a Q user. When you record a DIV (for example) in your account, the _DivInc gets automatically invoked.
AND, that an Income & Expense report (among others) will properly show them where you're requesting.
I'm not sure what you mean by Quicken needing to "find" the special categories. Everything with the code would stay the same except that in a report the special categories could have a parent. It might even work with minimal code changes by just allowing the special categories to have a parent.
This is standard functionality in accounting packages.
The _ categories don't show up where I want them in an income and expense report. Each special category shows as a separate line item at the bottom of the income section. It's kind of dumb that the _ categories can't be rolled up, but I can certainly live with it if it never changes.