How do I empty the trash?

[Alexey]

The used-space-filewalker is regulated by the option

@clement

--storage2.piece-scan-on-startup=true

or the analogue for the config.yaml:

storage2.piece-scan-on-startup: true

This is the default by the way, so you do not need to add it explicitly.
The lazy mode is regulated by the option

@clement

--pieces.enable-lazy-filewalker=true

this is again the default value.
The config.yaml analogue will be

pieces.enable-lazy-filewalker: true

If you would change these parameters with any of the ways, you need to restart the node (re-create the container for docker).