But that's how I do it
In the top panel, I select Attachments, the Manage Attachments window pops up, select the file, click Upload.
Then again in the upper Attachments panel and select the previously uploaded image.
And in the post there is, for example, [A T T A CH]94290[/ A T T ACH] (I added additional spaces)
K13_F2_5.jpg
and the image is normally visible