You can enable or suppress log messages for a particular log channel from within the editor using the following console commands:
Log LogName off // Stop LogName from displaying at the output Log LogName Log // Turn LogName's output on again
If you'd like to edit the initial values of the output levels of some of the built-in log types, you can use a C++ class to create changes for the engine.ini config file. You can change the initial values in the engine.ini configuration file.
See https://wiki.unrealengine.com/Logs,_Printing_Messages_To_Yourself_During_Runtime for more details.
UE_LOG sends its output to Output Window. If you'd like to use the more specialized Message Log window in addition to this, you can use the FMessageLog object to write your output messages. FMessageLog writes to both the Message Log and the Output Window. See the next recipe for details.