You just need to apply a tag to the Hero in a script. Pre-Level/10000 should be fine for this condition.
Code:
~ Turn on Flanking Condition
perform hero.assign[Condition.pstFlankin]
The above turns on the Flanking condition. To find the correct Tag for Concealment you just need to look at the tags on the Concealment condition. Once you find the correct tag id you just replace pstFlankin with the correct tag for Concealment.
From inside of Hero Lab go to the menu "
Develop->Enable Data File Debugging". If you are doing any editor work you want this option on.
Then RIGHT click on the "?" field of Concealment and select "Show Tags"....