Do I need to import something in order to use Modifier.weight()? I'm using alpha06

No, you don’t have to import anything. Make sure you are using it at right place like in Row or Column

https://github.com/vinaygaba/Learn-Jetpack-Compose-By-Example/blob/29a1ce7409f7fe0d2b48a049c2834b926787c2f6/app/src/main/java/com/example/jetpackcompose/layout/ViewLayoutConfigurationsActivity.kt#L130 but here they use it on a Button.

Here, the Button is inside the

Row

composable (Line no. 122) So,

Modifier.weight()

is used here from

RowScope