Sure, this is possible. Please check under File > Preferences > Report Design > Preview to enable the external browser. This should allow you to see the preview within your browser and without being connected to the internet.
I have the same problem, the Preview tab in the Report Designer is always blank. I've seen this to work in older versions (a few years back). I'm using 2.10.1 on Windows 7 64-bits.
How should I configure my preferences for the Preview tab to work properly?
Thanks again for reporing this problem which boils down to an issue in the BIRT integration related to Windows 7 and 8 systems and IE11. The provide workaround seem to work and we will incorporate it into KNIME with 2.11 released in December. If you can't wait you would need to add the property
-Dorg.eclipse.swt.browser.IEVersion=10001
to the knime.ini file and replace or delete the registry entry: