If you want to pass geometry as text you need to extract the geometry as text, so choose FME xml or WKT or any text based format in your geometry extractor instead of FME binary

Ah brilliant, thank you. Yes the FME xml worked!

I agree with @ebygomm​ . In addition, I would recommend you to use "Hex Encoded FME Binary" if you need to perform completely loss-less encoding/decoding.

Thank you, that's helpful and works really well. Do you know if it's possible to include the coordinate system within the Hex Encoded FME Binary, or if I will need to pass that as a separate parameter?

I don't think it's possible to include coordinate system definition within geometry text. You will have to create another user parameter to pass the coordinate system name.

Alternatively, a pair of Recorder and Player could be a workaround.

In the main workspace, use a Recorder (Recording Mode: RECORD) to save the feature into a file and pass the file path to the child workspace through the WorkspaceRunner. You can then use a Player to read back the feature in the child workspace.

If you do so, you can restore the whole feature including not only geometry and coordinate system but also all the feature attributes.

Thank you, I'll take a look