The Search All command mirrors the Text Filter dialog's configuration options with one exception - you cannot restrict your search to a particular log file column. When searching all log files, searches will always be performed against the original log entry.
The Search All command is not a filter and it works more like a traditional search box found in most applications. Search results will be displayed in the Search Results window with results grouped by the log file where they were found. For example:
Here we can see the search 'transaction' was matched in two separate log files with 5441 matches per log file.