Unfortunately the new docker applications framework was found not to support migration of the apps pool in the way we had it implemented with kubernetes in 24.04. This checkbox has been removed for 24.10.0 and we are looking into a method to replace the functionality in a future release.
In the meantime, if you want to change the apps pool location, you can either delete the existing apps (with the delete ix-apps checkbox selected) to clear the existing app data and then reinstall applications on the new pool. Or you can change your pool and accept that some apps will continue to remain on the old pool for now.