There is a way to make the Codewarrior IDE work with a third-party editor. The setting is under the IDE's preferences. Choose Edit | Preferences, and then select the IDE Extras panel. There is an item labeled Use Third Party Editor that you configure to make the magic work. For more information, consult the 8_16bit_IDE_User's_Guide.pdf manual that came with your CodeWarrior installation. Check chapter 21, Prefeences and Target Settings, under the "Launch Editor" section.
For creating make files, consult the Build_Tools_Utilities.pdf manual. Study the chapter titled Maker: The Make Tool for more info.
---Tom