I have found one use of "unique digital window" in an academic text (below) but even that is placed inside quotes.

That is to say, a paradigm that does not necessarily involve an office or a ticket desk that must be opened is being consolidated, but rather that the citizens-Administration relationship is intertwined in the light of the concept of a single digital portal or by the so-called “unique digital window”.115 It is a phenomenon that in Argentina is grouped under the denomination of “integrated approach of government” where the digital services “go” towards the computer or towards the mobile device of the citizens.116 That is why it is so important to recognize the fundamental right to relate digitally with the Administration. In this regard, it is useful to highlight a fairly recent and novel example that occurs in the area of the Autonomous City of Buenos Aires.
https://www.researchgate.net/publication/327146580_Digital_a...

Also I am not convinced by the quality of the translation either so I have opted for more of an explanation.

From my browsing it appears that this phrase is used in relation to many different things, not just music copyright. I have found 'ventanilla unica digital' related to local government, education, shops... it basically refers to any digital portal giving you access to online information.