Making drop shadow edges soft?

I use plane only for demonstration. here is some recommendation how to do glow in Adobe Dimension. 

Certainly! In Adobe Dimension, you can create glowing light effects using different techniques. Here are a few ways to achieve that:

Environment Lighting:

Use the image-based lighting layer system to create custom environment lighting. Environment lights evenly illuminate all objects in the scene, regardless of their size or position.

Objects can’t get closer to, further from, or behind the environment light, ensuring consistent lighting and shadows..

Emissive Materials:

Turn any object into a light source using emissive materials. This is useful for practical purposes (e.g., making buttons glow) or creative effects (e.g., luminescent worlds).

Sun Light Cloudiness:

Adjust the cloudiness value for the sun. Low cloudiness produces hard-edged, crisp shadows, while high cloudiness disperses sunlight through atmospheric elements, creating soft, faded shadows