In Shopify theme editor you can go to App embeds and search for Whatmore.
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Once you expand that by clicking the downward arrow, you can see multiple customization options. Scroll down to find the below options
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- Minimized Video Position (Mobile)
- Minimized Video Position (Desktop)
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You can change the position by changing these options, for example here, I'll chose right for the "Minimized Video Position (Desktop)" which will change the default position of the floating video to the right side.

Thus, the floating video position is changed, similarly you can change for mobile user, by changing the "Minimized Video Position (Mobile)" option.