Intellisense

Completion, definitions, and hover draw on your whole project, not just the file you have open.

Where to find it

In the editor: Always on in the source editor Suggestions appear as you type.
Shortcut: Ctrl+Space Open suggestions.
Shortcut: F12, or Ctrl+Click Go to a definition.

The source editor completing a citation with bibliography keys and titles

What completes

Completion covers both what LaTeX ships with and what your project defines.

Commands and environments, including your own \newcommand and \NewDocumentCommand definitions.
Package and class names, with each package's options and key-values.
\ref labels, shown with the number they will resolve to.
\cite keys, searchable by title and author, plus glossary entries.
File paths inside \input, \includegraphics, and \addbibresource.

Across the whole project

Macros are gathered from the main file's chain of \input and \usepackage, so a chapter fragment is understood with the same definitions the main file has. Labels and citation keys come from every file in the folder.

Definitions and hover

Go-to-definition and hover work across files, so following a macro to where it is defined does not depend on it being in the file you are looking at.

Arguments and renames

Accepting a macro that takes an argument reopens the suggestions for that argument. Renaming or moving a file updates the references pointing at it.