I have made a drawing that uses a number of “In Model” components (i.e. not imported) that I made. I then decided to redo one of them completely. Rather than use the Edit Component mode, I redrew the new model from scratch. Then I tried “saving” it using Make Component command and gave it the same name as the old one, thinking I would get a message asking if I want to replace the old component with the new one. Instead, I got a message saying that my new component name already existed and I should use a different name. But really I would just like to eliminate the old component completely and use the its name for the new one. I can’t find out any way to delete an existing component. I would think that there is a way to do it so people can avoid their Sketchup drawings from accumulating junk. Any suggetions? I use a Mac with OSX 10.11.5 and Sketchup 2016.
You could copy the geometry from your new model into the old component, then save the changes. Just copy the new stuff, open/edit the old component, delete all its geometry then paste the new stuff into the same space.
However, normally, when you try to save something new with an existing component, you are asked if you want to update the existing component definitions (if you have that component still present in the model. That would work too. If you don’t have that component in the model, you should just be able to purge or delete it from the component palette, then create a new one with the old name
If I understood your question properly, this GIF will be helpful.