just some of my thoughts about the global search app.
Instead of having to choose between “collection” and “all data”, you could use a kind of query language to search only specific data/indexes.
So, for example:
if you only want to search in the codex: codex:"climate change"
if you only want to search in orders:: orders:“climate change”
Maybe you know the app “Alfred” for Mac OS, where you can define your own so called file filters. Or does that make no sense from a usability point of view?