After updating to macOS version 10.13.3, you may face certain issues with the system’s performance. One of the problems might be the inability to insert photos into a sub-folder. It is rather irritating because the owner of Mac has to paste every pic manually instead of having them all copied to the target sub-folder. It is not possible to add pictures using iPhoto to a personal blog as the app provides just iPhoto items to choose from.
Simple as ABC
The answer the question could be as short as a couple of sentences. Looks like you just don’t know the peculiarity of ‘Save As’ menu in macOS. The thing is, initially, it shows up in a compact mode? Like in the picture below:
But once you click on the tiny arrow key near the ‘Save As’ field with the file name (circled in red), the window will expand and show the detailed save dialogue:
Here, you can habitually browse your hard drive and pick whatever location you need.
So, basically, the issue is not with your Finder or iPhoto, it’s just the non-intuitive macOS interface.