更新时间:2023-12-04 22:51:04
As of January 2021, you can set auto fit setting in Google Slides editor.
When you click inside shape, you can see new Auto-fit setting, set to "Do not autofit" by default:
You can change it to "Shrink text on overflow":
Or another option: "Resize shape to fit text":
P.S. there seems no Apps Script changes available for this new option at the moment.