Please open ForeFlight and open the Aircraft W&B profile you want to edit. Once open, select the LOAD button in the left column on the bottom and then select EDIT just to the left of the Load button. Now, find the Line Item you want to move and tap and hold on the three lines to the right of the Line Item description. A shadow will appear under the Line Item meaning it is selected to move. Now, swipe your finger to move the Line Item to another Station. Let go by removing your finger from the screen.
It is useful to know that when moving a Line Item from one Station to another, that the Arm used for that Line Item will be the one associated with the Station it is under and not the old Station.
You will see that the CG shift between images 1 and 2 was caused by the shifting of the weight of the Line Item to another Station.
Image 1. How to move a line item to be under another station.
Image 2. Notice how the CG shifted since the line item now falls under the arm of the new station.