Hm, this one we will need to think about/get feedback on.
I think my original idea for this wasn't temp as in NXF_TEMP but rather scratch: https://www.nextflow.io/docs/latest/process.html#scratch
That 'makes sense to me' (a local scratch/temp on a compute node), but I'm not sure what NXF_TEMP does...
My feeling is that NXF_TEMP might be for the nextflow command itself, which is why it doesn't have a specific 'scope' equivalent and thus not be relevant for us here...
Do you want to ask on the nextflow slack/discourse what the difference, and then we can update accordingly?

But otherwise (assuming it's OK to set NXF_TEMP): You could try auto0-detecting if NXF_TEMP is already set and use that to provide a default to the user (see my draft PR how I do it, or could wait for that to go in and re-use the functions)

Otherwise worked for me :)