Explanation:

MDT is a tool that allows you to automate the deployment of Windows operating systems and applications. To install an application for all the task sequences that deploy a Windows 11 image, you need to perform the following three actions in sequence:
* Add App1 to DS1. You can use the Deployment Workbench to import the executable installer of App1 to a folder in your deployment share. This will create an application entry with a unique GUID that identifies App11.
* Identify the GUID of App1. You can find the GUID of App1 by opening the application properties in the Deployment Workbench and looking at the Application GUID field1. You can copy the GUID to use it later.
* Modify CustomSettings.ini. You can edit the CustomSettings.ini file in your deployment share to specify which applications to install for each task sequence. You can use the Applications property to list the GUIDs of the applications you want to install, separated by commas1. For example, if you want to install App1 and another application with GUID {1234-5678-90AB-CDEF}, you can use this line:
Applications={GUID of App1},{1234-5678-90AB-CDEF}
These are the three actions you need to perform to ensure that App1 will be installed for all the task sequences that deploy the Windows 11 image from DS1. I hope this helps you.
If you want to learn more about MDT and how to deploy applications with it, you can check out these resources:
* Get started with the Microsoft Deployment Toolkit (MDT) (Windows 10)
* How to deploy applications with the Microsoft Deployment Toolkit