Hello,
In the following documentation there is no mention how or if URL Filtering works with relative Dates at all:
https://docs.microsoft.com/de-de/power-bi/collaborate-share/service-url-filters
We would require something like:
filter=Table/Date in this day
Can someone elaborate if there is an operator for this available?
You can do that (partially) with a calculated column but in general you are correct - relative URL filters are not supported in the way that - for example - Salesforce.com does it ("Last30Days" etc). Even when you specify relative filters in Power Query it will actually be translated into absolute filters during the query folding stage.