You must add the x-experiment field to the Log Processing.cfg file, which is used to create an extended dimension.
To modify Log Processing.cfg
In Insight, open the Profile Manager by right-clicking within a workspace and clicking Admin > Profile Manager, or by opening the Profile Management workspace on the Admin tab.
In the Profile Manager, click Dataset to show its contents.
Right-click the check mark next to Log Processing.cfg and click Make Local. A check mark for this file appears in the User column.
Right-click the newly created check mark and click Open > in Insight. The Log Processing.cfg window appears.
Click Fields to show its contents.
Right-click the last field in the current list and click Add new > Field.
Type x-experiment in the newly created field, as shown in the following example:
Right-click (modified) at the top of the window and click Save.
In the Profile Manager, right-click the check mark for Log Processing.cfg in the User column, then click Save to > < profile name> to save the locally made changes to the working profile.
The dataset begins reprocessing immediately.
For more information about Log Processing and Fields see the Dataset Configuration Guide.