Awkward, but it works.
You'll need to use the Advanced editor. Using the image icon, and the Basic Uploader, upload your image as usual. Doesn't matter if it's remote or on your machine.
Next, scroll down and look for the Manage Attachments button and click to open another window:
At the bottom of the new window, the attachment (the image you uploaded) will be located in the left of the frame. Hover over it, and use the "X" to delete the attachment. DO NOT delete files in the top frame (previously uploaded files). Use the "X" on that window to close it (don't use the "Done" button at the lower right of the window), and you're done.
Having already placed the image object in the "Your Message" editor window, it will still show in your post, but without the duplicate image showing the attachment.
I used that method to post a picture of my Pontiac here:
https://forums.hamisland.net/showthr...l=1#post594619
and on the graphic of the Manage Attachments button in this post.
Like I said, awkward. No warranty implied!