Make a shortcut to your "da2.exe" file (typically located in the C:\Program Files (x86)\Dragon Age 2\bin_ship folder) on your desktop, Start Menu, or wherever. Right click on the shortcut, choose properties, then add the following to the end of line in the "Target" field: -enabledeveloperconsole — it should look something like this:
"C:\Program Files (x86)\Dragon Age 2\bin_ship\DragonAge2.exe" -enabledeveloperconsole
Do not remap keys in game for a quick console access key as in Origins, it will not function properly.
Ok maybe not as helpful as I thought... I think it is the tilde (`) button. The console in invisible so you need to press enter after typing the command to enable it and go back to the game... apparently. I am about to try it.