You can use the picture-in-picture (PiP) tool to place a smaller video clip or image on top of the mainframe of your project in Clipchamp.

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Here is how to do it
Add a video, gif, or image to the editing timeline.
Select/ highlight the item.
The layout panel will appear above or near the preview screen.

Click it to enable PiP.
Then, move the item onto a 2nd row on the timeline above another image or video you want it to appear on top of:

Click the icon again to see the placement and size options:
The following shows the steps in sequence:

This feature is available to test on free accounts and available to fully use on the Business and Business Platinum plans.