Dear Ithatz,
1. you can navigate the file explorer one hierarchy level above the folder that contains the methods so that the software can recognize it.
2. if you are looking for processes for sludge and food waste, maybe check the process folder called 'E:Water supply; sewerage, waste management and remediation activities'. if you type 'sludge' in the search window, a number of flows and processes appears (not sure what type of sludge you are looking for). for food waste, you can find some processes and flows with the term 'biowaste'.