Say that I already have a PBI report which is posted to the service/workspace. I want to use the same dataset and Query, but build new visualisation to make a different/additional report. Is it possible to make a copy of the pbix file and publish it to the service with a new name without affecting the original PBI report?
Yes, you can save a copy of the report, either by opening the report and click on File -> Save a copy:
or by using the ellipsis button in the workspace itself:
This will make a copy of the report, but it will use the original dataset (i.e. there will be only 1 dataset and 2 reports).
You can also create a new report and use the original dataset as a data source.
And of course, you can download the report, rename it, and publish it again (in which case you will get a copy of the dataset too).