The UMS ID is required by the enhanced Automatic License Deployment (ALD) feature that has been introduced with IGEL OS 11.
In opposition to the legacy ALD which uses ALD Tokens (see How to Set Up and Use Automatic License Deployment (ALD)), registering your UMS ID on the IGEL Licensing Portal once saves you transferring an ALD Token for every single Product Pack.
You can perform the following actions with UMS IDs and Product Packs: