The Duplicate & Repeat tool is arguably one of the most powerful, least understood features of Tinkercad. Don’t think of it as a way of simply copying objects (copy and paste can take care of that). What makes the Duplicate & Repeat tool so special is that it duplicates not just the selected object, but the actions you've taken on the object. It takes some time to master, but once you do, you’ll feel like a pro.
For example, by duplicating and repeating size, workplane, and height adjustments, you can create a pyramid in seconds.
Duplicate and repeat angle adjustments to quickly create a flower pattern.
Duplicate and repeat a sequence of height, size, and angle adjustments to create and organically curving monster tentacle.
The following video by LinkedIn Learning demonstrates the process step-by-step, along with a variation using Tinkercad's mirror tool.