Yes the CM345S will convert from SCART to VGA, but if you're going to buy that screen then you won't need it. The screen has both VGA and SCART inputs, so will display 15KHz and 31KHz screens. All you will need to do is connect the Amiga's RGB output to the SCART connector with the cable I linked to, whatever your VGA source is to the screen's VGA input, and then switch between the RGB and VGA inputs on the screen depending on which display you need to see.
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moto