Keyboard shortcut to refresh Gradle project in IntelliJ IDEA

You can use "Refresh external project" (for currently selected) or "Refresh all external projects". These actions are available in the find actions menu (CtrlShiftA) and can also be assigned a shortcut in the keymap settings as there is no default assigned.

Note that the menu item when right-clicking a Gradle project in the tool menu is also labeled "refresh external project".

There is no option to assign shortcut to refresh just gradle projects.

However, there is an action "Refresh all external projects", which will trigger also refresh of gradle projects.

You can set the shortcut in

Preferences → Keymap → Refresh all external projects → Right click → Add keyboard Shortcut

In newer versions of IntelliJ Idea, the name of this functionality has been changed to Reload All External Projects