Hi, I keep getting this error

Could not get unknown property 'kotlin_serialization' for object of type org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler.

while importing this dependency

implementation "org.jetbrains.kotlinx:kotlinx-serialization-core:$kotlin_serialization"

It must be declared in

gradle.properties

, like here.

Ok done. How do I sync Gradle files again? there is no option popping up.

Refresh button - first

Alright, thanks!