There is no inbuilt function for this as stated.
You can use Package Manager installed in both profiles, https://f-droid.org/en/packages/com.smartpack.packagemanager/
Export in one, transfer the bundle whichever way you choose and install in the owner. I use this to install stuff from the Play Store in an isolated profile and pull it back. I use a local ftp app temporarily for file transfer. It's a bit redundant and the install ends up being mostly a no-op since it's installing the exact same app twice but it works. This is particularly necessary for very dynamically delivered apps from the Play Store which have various device specific APKs in the bundle.