Hi Thomas. Welcome to the forum!
Really sorry you are having problems. When you specify a file in the Traces/(e)SWC file field, the plugin makes a list of all the files found on the directory where the specified file resides, and uses it to automatically populate (by educated guess) the Image file field below in the prompt.
I haven't looked into it yet, but in your case, it seems as if the plugin is not detecting
.traces files in the path you have specified. A couple of reasons could be: files have unexpected extensions, are seen as hidden, or perhaps are in a remote server? Is any of these the case?
That being said, this is just a convenience feature (almost UI gimmickry). It does not need to be used when calling the plugin from a macro. We could try to debug it, or I could just disable it when the plugin is being called by a macro or script. Would that be OK for you?
You can monitor the progress on this issue here. I will try to look into it quickly.