https://github.com/JetBrains/compose-jb/blob/master/gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/ComposePlugin.kt#L52-L56 - Where can i see the source code of these dependencies?

These are basically the MPP variants of the compose desktop source, which you can find in the androidx repository: https://cs.android.com/androidx/platform/frameworks/support/+/androidx-master-dev:compose/ui/ui/src/desktopMain/ The pom files point to the appropriate dependencies (like builds of skiko) for the particular platforms.