Below are the steps:

1) On the Source Range column, click the “Set Inline Range From Drawn Shape” tool, as shown below.

2) Digitize the targeted polygon, then right-click when finished. Below is a sample of polygon’s digitizing result.

3) On the Source Range feature, add New Text Range. Copy the nodes recorded on “Inline” tab, then paste it to the new range. Name it (e.g., Polygon) and click “Select”.

Below is the result: