After syncing your email to SFMC as a Template-Based email, your dark mode images are fully editable
You can swap out each image, change the alt text and change the link as you normally would
They will appear in the SFMC editor as two separate images so that you can edit them
You must edit both images individually to make any changes. For example if you need to change the link on the image, you will need to change it on both images to ensure they both link to the same URL.
Note that while you’re using SFMC, if your operating system is set to dark mode, SFMC will show you the dark mode version of the email in the preview and editor panes. If your operating system is set to light mode, then you will see the light mode email.
You can edit both images in either mode.
If your operating system is in light mode
When editing your email, hover over the visible image, which will be the light mode image if your operating system is set to light mode. Click to edit as you normally would.
Underneath the light mode image, there is an editable content block that you can hover over. This contains the dark mode image. Click this block to edit the dark mode image as normal.
Note that this editable area creates a gap while you are editing, so that the clickable block is large enough to see. The gap will not be visible in the final email, which you can see when you preview the email after saving.
If your operating system is in dark mode
If your operating system is in dark mode, everything works the same but the order of the images is reversed. So when you hover over the dark mode image, you can click to edit it as normal:
And above the dark mode image is the editable content block that you can hover over. This contains the light mode image. Click this block to edit the dark mode image.