It's been almost a year since I reported having troubles with StoreSetMetadata() and it's time to revisit this. The function now exists meaning I no longer get a reference error when calling StoreSetMetadata(). However, I believe it's still not working correctly. Below is some example code:

/*** assuming we set our S3 credentials in Application.cfc and the bucket has the correct policy for downloads ***/

param name="url.filename" default="test.txt";
myFile = "s3://mybucket/#url.filename#";

fileWrite(myFile,"Sample s3 text");
StoreSetMetadata(myFile,{
"Content-Type":"text/plain",
"Content-Disposition":"download"
});

writeOutput('<a href="https://s3.amazonaws.com/mybucket/#url.filename#">download</a>');
writeDump(StoreGetMetadata(myFile));

When I run this code in ACF11 it downloads fine and when I log into S3 I can see permissions are changed. However, when I run this in Lucee5 the dump shows the meta data as being set but in S3 the permissions are not actually changed and when I try to download it just takes me to the page instead of downloading. Again, I'm not getting any errors anymore but it doesn't seem to actually be setting the Metadata on S3.