Two ways come to mind:
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have a second video track with a transparent-background PNG image that has a Rotate filter applied to it, like so:
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if you want to get really fancy with animations and such, and you’re not afraid of CSS and/or math, you can use the Overlay HTML filter to do all sorts of cool stuff, as user jonray has been posting about in threads such as this: Creating video title animations in Shotcut using the Overlay HTML filter
