The feature is not brand-new. However, it is still not well-known.
For standard reports in Google Analytics user interface, it is common to use primary and secondary dimension. For example, Source/Medium report interface looks like this:
However, the interface does not allow you to use third dimension for your reports.
There are several solutions for that, depending on the goal of your analysis. You may use a segmentation feature and segment your data based on a specific dimension you intended to use. Another solution is to use API for this.
However, Google Analytics online interface allows you to use a third dimension. In fact, it allows you to use even more dimensions.
How to do it?
Go to Custom reports.
Here, it is necessary to open “Flat Table”, next to “Explorer”, which is a default report.
The custom report allows you to choose third dimension, forth dimension and fifth dimension.
In this way, it is possible to create multi-dimensional reports. However, it is necessary to take care of the amount of data you have for your analysis. Every dimension results in a greater level of segmentation of data and it may influence the amount of data for every category. Therefore, it is necessary to work with multiple dimensions in a reasonable way.