I figured it out finally. In order to bring it into Data Inspector, you must choose open dataset and select the DGNV8 dataset. Then select your file, and open it up. The full steps are,

1. Open your seed file and place a text element on a different level for each text style you wish to add. I suggest making the text element the same as the name of the text style it is being placed on.

2. Open Data Inspector and under the file menu, select "Open Dataset".

3. Choose the Bentley Microstation Design (V8) (DGNV8) format. Then use the button to the right of the dataset entry to select your file and click OK. Depending on your parameters, this may take a few minutes.

4. Once the file is open in Inspector, select an element within and locate the igds_textstyle_id in your feature information.

5. In your workspace, use an AttributeCreator to set your attribute name to "igds_textstyle_id" and set the value to the text style number you found within the inspector. NOTE: This also works for figuring out the integer value for "igds_justification" and just about any other igds format attribute you would need.