Do not search for version 7.15. It is backward compatible with Mule 4 applications. If you are working on an existing project that demands an older runtime, you can install older Mule Runtimes inside the new Studio version via the "Install New Software" menu.
-startup plugins/org.eclipse.equinox.launcher_1.6.400.v20210924-0646.jar --launcher.library plugins/org.eclipse.equinox.launcher.win32.win32.x86_64_1.2.400.v20211117-0650 --launcher.defaultAction openFile -vmargs -Xms512m -Xmx2048m <-- Increase this to 2048m or 4096m if you have 16GB+ RAM -Djava.net.preferIPv4Stack=true -Dfile.encoding=UTF8 -Dosgi.requiredJavaVersion=1.8 anypoint studio 7.15 download
Since "7.15" is unavailable, you should download (Standard for Mule 4). Do not search for version 7