Adobe Photoshop CS5 and CS6 unable to save file and prompt below error:
Could not save as FILENAME because the file is already in use or was left open by another application. Photoshop CS6 is running on macOS Mojave. In macOS Mojave, there are problems saving files within Photoshop CS 6 & 5 due to incompatibility with APFS. Try to follow the below steps to create a virtual disk and save in it.
Save the file in the new disk image
Step 1: Open Disk Utility > File > New Image > Blank Image.
Step 2: Give the virtual volume a useful name, set the size big enough to edit images or batches of images, but small enough to fit onto the machine. Check the virtual disk format is Mac OS Extended.
On macOS Mojave, this issue seems to revolve around the thumbnail display in the Finder. Check if you have a folder open with that file clicked or selected, the image is displayed as a preview in the Finder. Selecting any other file or closing the folder may fix it.
Uncheck Save in Background option
Step 1: Open Photoshop, and choose Edit > Preferences > File Handling.
Step 2: Uncheck Save in Background option.