I'm rewriting this answer, as @kleopatra pointed out it was inexact
For suggestions to work, you need to have JavaFX on your project's build path.
If you've created a plain Java project in Eclipse, with a module-info.java at it's source path root, then you need to add all the required jars to the module path:
- JavaFX SDK should already be installed on your system, or download it from Gluon and unzip it
- Right-click your Java project, got to Build Path -> Configure Build Path...
- Go to Libraries tab, point to the Modulepath section
- Click [Add External JARs...] button, pick all the jars from JavaFX SDK, hit [Apply and close]

Then suggestions should work as expected, and import
s will be automatically inserted at the top of your java files, but they will appear in error the first time you import anything from a given library module, as this module must also be required in your module-info.java. You can do that automatically with a quick fix ("Add 'requires javafx.something' to module-info.java") when hovering the import
.
Now there's a more straightforward way to create a JavaFX modular project in Eclipse, using Maven:
- Create a new Maven Project
- Check and pass the first wizard screen
- Select archetype
org.openjfx:javafx-archetype-fxml
- On the next screen, you can select the JavaFX version of your choice (currently 13 by default)
After the wizard terminates, you've got a nice little project already setup with an application window and two FXML sample displays. You can start from there to build your own project.

