Meld's preferences

Editor preferences
Editor command

The name of the command to run to open text files in an external editor. This may be just the command (e.g., gedit) in which case the file to be opened will be passed as the last argument. Alternatively, you can add {file} and {line} elements to the command, in which case Meld will substitute the file path and current line number respectively (e.g., gedit {file}:{line}).

Folder Comparison preferences
Apply text filters during folder comparisons

When comparing files in folder comparison mode, text filters and other text manipulation options can be applied to the contents of files. If this option is enabled, all currently enabled text filters will be applied, the blank line trimming option will be applied as appropriate, and differences in line endings will be ignored.

Enabling this option means that Meld must fully read all non-binary files into memory during the folder comparison. With large text files, this can be slow and may cause memory issues.

This option only has an effect if "Compare files based only on size and timestamp" is not enabled.