In PackEdge / Plato, once the SmartMarks are added to the list, it's difficult to move their position up or down in the list.
If you add any SmartMark to the SmartMarks window, it's not possible to move them up or down in the list. If you do it, the SmartMark will become "dependent" on the other SmartMark where you attach.
There is no solution for this issue at the moment.
There are two workaround to manage to solve this problem. The first one is to manually write a "schema" how the SmartMarks set should look like on the file, then start adding the SmartMarks, keeping in mind that they are always added at the top of the list.
The second workaround is to Cut (CTRL + X) and Paste (CTRL + V) the SmartMarks. Once you paste them they will be always placed at the top of the list, attached at the Trim Box or Media Box, as you defined.