The Logging page in File > Preferences... controls how much LanSend records and whether it also writes a log file to disk. File logging keeps a record after you close the app, which helps when you need to look back at a delivery problem or hand details to support.

Minimum level sets the lowest level that appears in the Application log tab. Anything below the level you pick is dropped. Raise it to cut noise, lower it to capture more detail while you track down an issue.
Tick Enable file logging to also write the log to disk. The file gets its own minimum level, separate from the in-app log, so you can keep the tab quiet but still save full detail to a file.
The remaining fields control the file itself: