UICodes wrote:is there a further IM command to introduce these chunks into the image?
Drarakel wrote:I think that directly writing the file as palette PNG [...] is not possible with the current IM versions

You could test some older ImageMagick versions though.
In IM v6.5.8-5, for example, simple commands like these are successful and write a palette PNG with tRNS chunk:
convert img.png -transparent "#FB00FF" -type PaletteMatte img2.png
convert img.png -transparent "#FB00FF" -colors 256 img2.png
(I would prefer the first command as the color reduction parameter can be a bit more risky.)
Result:
