You cannot translate a slot. Slots don't have a position.
When you select a slot in the tree, the attachment visible for that slot is selected in the viewport. If no attachments are visible, the parent bone for that slot is selected in the viewport.
When you select an attachment in the tree that is not visible, the parent bone for that attachment is selected in the viewport. This is what you are seeing: you select attachments that are not visible, so the parent bone is selected in the viewport. Then you move the parent bone and it appears that all attachments under that bone have moved.
If an attachment is not visible, it cannot be manipulated in the viewport. If you want to move many attachments that are under the same slot, you may want to temporarily drag them to a bone, which will create a slot for each attachment. Now that all the attachments are visible at the same time, you can select them all, move them, then drag and drop them back to the original slot and delete the now empty slots that were created.
Note that using image compensation does change all the attachments at once. If you want to move the parent bone but have the attachments appear to stay where they are, use image compensation.
