The Unity Inspector, for all its usefulness, does not support dictionary serialisation (i.e. can't display dictionaries). Moreover, though it supports automatic list serialisation, sometimes you want to be able to reorder their elements.
Multiple solutions, both free and commercial, exist to fix these problems. Inspector add-ons, list frameworks, the lot; some more convenient, useful, or convoluted than others.
Well, here's another one. This little kit is free and supports both reorderable lists, as well as reorderable dictionaries. You can get something like this:
This repo is convenient, it's based on a well-known implementation, and most importantly, allows you to have reorderable lists and reorderable dictionaries without having to run two separate implementations, as is so often the case.
Usage details can be found on the github page.