I mean, we could refrain from talking about the need to "jump around," but that's the crux of the issue: modern IDEs (like vscode) include "peek" functionality to look at a definition inline. No need to jump around at all. And a thousand-line component has a thousand lines of context it could be pulling in; reasoning about that level of complexity rapidly gets complicated.

If you have some complicated expression to say inline in a React declaration, pull it up to the preparatory layer. If there are performance reasons not to do that, push it down into a subcomponent.