Be able to change the center of mass for compound rigidbody created in editor

Description

Compound dynamic bodies created in the editor are behaving very oddly. Even if there is only one child and that child is setup the same way as a regular primitive rigidbody, the behavior it very different. The way they are interacting with other bodies and the way the editor displays the bounding box of the compound bodies incorrectly makes me believe it's a scaling issue for the children collisions, but I'm not sure.

Here is a sample project for build from master and last major version, both have the same issue: 1.27.0 and 1.28.0

The falling chair demo uses compound dynamic rigidbodies but they're created programmatically, which is what makes me think it is something specific to the editor.

Steps to Reproduce

1. Create new project
2. Create a dynamic rigidbody in the editor and something for it to interact with (floor)