Simple Mesh Bake allows you to combine multiple meshes by pressing a single button, which can often help when building levels from assets and using a bunch of static uncombined meshes. To Bake just open the Simple Mesh Bake window, add the desired meshes to list and click on the Bake button. After that, the system will automatically combine all meshes, optimize the use of materials and give the finished result in the form of a new object on the scene and a file in the Assets folder. Use it!