Styles not copied when moving documents between projects

Create a custom style in project 1.

Apply this to some text in a document in project 1.

Drag that document from project 1 to project 2.

That text no longer has the style applied to it (it keeps the formatting, but not the style).

That means you can no longer do things like find by style or globally redefine the formatting for that style.

You need to import the style first:

Format > Styles > Import Styles…

That’s how it works on the Mac, anyway.