Yes, this is possible.
If the app is set up and already controls a SmartHome box for home, for example, another SmartHome box can simply be added to the same account, for example for the vacation home. To do this, call up the settings in the app. Under App Settings, click on "Current device".
Via the plus sign, another SmartHome box can be searched for and added to the account.
Important: In order for the device to be found, you must be on the local network. Click on "Next" to enable the device for remote access if necessary.
From now on, you have the option to simply select the desired SmartHome Box in the settings if necessary.
You also have the option to manage multiple user accounts in one Rademacher app. If you want to edit an installation of an acquaintance as well, you can add another account in the Settings area "current user account".