General info on overlong scan times and how to improve them is available e.g. here:
- Greenbone Enterprise Appliance documentation: 10.13.2 Long Scan Periods
- Greenbone Enterprise Appliance documentation: 20.1 Why is the Scanning Process so Slow?
- Greenbone Enterprise Appliance documentation: 17.2 Optimizing the Scan Performance
There is a scanner preference (via openvas.conf) called log_whole_attack which can be set to yes so that the execution time of each plugin / VT is logged accordingly in the scanner logs or syslog.
AFAICT there is no such functionality included in any component of the Greenbone Community or Enterprise Edition.