If you create the WindRose plot by the Binned Data, you can try to: 1. Add the new column in the worksheet, and enter the percentage value. 2.Right-click the new column and select "Set As: Label" in the context menu.. 3.Active the Wind Rose graph, and select "Graph: Layer Contents" in the main menu. Then select that new column in the left panel of the "Layer Contents" dialog, and add it to the right panel. Click "OK".
Please note: if the percentage value is calculate by the dataset in the worksheet, you can try to use the "Set Column Value" tool to calculate it.