I finally found a way to avoid a pillar on the left side when using the Crop&Zoom function under Power Tools. I wanted to crop to reduce the proportion of sky to ground in a 50 second clip for uploading to Shutterstock. At first I placed the crop zone in the lower left corner. That resulted in a pillar on the left side. Then I centered the crop zone from left to right. That resulted in a video with no pillar on either side.
(My source file is in 4K at 30fps. I am using 16:9 Aspect Ratio during Edit mode, with 15 Video Stabilizer and 30 Video Enhancement. In Produce mode the Output is set for the same resolution and frame rate to deliver an mp4 file at 50Mbps.)