Many people want their Photoshop derivatives to be stored with the raw file it was created from, so that’s why it works that way by default: If you use the Edit In command from Lightroom Classic, it’s assumed you want the derivative both in the same folder and in the same catalog. If you don’t want it to work that way, the answer is to use an alternate method instead of Edit In.
It’s unclear whether you want the Photoshop derivative (A) stored only in the folder on the external storage volume, or if you also want (B) the Photoshop derivative kept out of (not tracked by) the Lightroom Classic catalog. But it’s possible either way.
If you want (A):
- Continue using the command Edit In > Open as Smart Object in Photoshop. Saving the resulting Photoshop document will automatically added to the same folder as the raw original.
- In the Folders panel in Lightroom Classic, drag the Photoshop document to the folder on the external storage volume. That will both move the file on the external storage volume, and update its tracked location in the Lightroom Classic catalog.
If you want (B), do not use the command Edit In > Open as Smart Object in Photoshop. Instead:
- If you have made any edits to the raw file, select the raw file and choose Metadata > Save Metadata to File (in the Library panel) or Photo > Save Metadata to File (in the Develop panel). Or just press its keyboard shortcut Command-S.
- From the Filmstrip or Grid, drag the thumbnail preview of the raw file, and drop it on the Photoshop application icon (or an alias of it), or in the Photoshop application window.
- In the Camera Raw window that appears, click Open.
- Edit and save the Photoshop document to the folder you want.
Because this method doesn’t use the Edit In command, you open the document behind the back of Lightroom Classic. It will not notice what you have done, so it will both be saved in the folder where you wanted and it will not appear in the Lightroom Classic catalog (unless you run Synchronize Folder on the folder you put it into).
A complication is that you have been opening it into Photoshop as a Smart Object, and my (B) workaround doesn’t do that. If you must use it as a Photoshop Smart Object, add these steps to workaround (B):
- First, in Photoshop, create a new document of the same pixel dimensions as the raw file, and leave that document open.
- When you drag the raw file thumbnail preview from Lightroom Classic in step 2:
- If you want it to be an embedded Smart Object, drop it in the Photoshop document.
- If you want it to be an linked Smart Object, hold down the Option key as you drop it in the Photoshop document.