First of all you dont need another worksheet for the approval process. Increasing worksheets only increase clutter and makes it hard for the app to work fast.
You keep all those approval process columns within the leave table, using REAL columns. Make two slices from the table, one just containing the leave process columns, another containing the approval process columns. MAKE SURE TO INCLUDE THE KEY COLUMN IN BOTH SLICES.
Make views from both of them. The leave slice would be used by the general users, the detail view of the whole would be used by people higher up, and a form view from the approval slice would be linked from that detail view by
LINKTOROW([Key column_Name], “Form View name that is made from the approval slice”)
Any data change action, like changing status column, can be attached to the form saved of that view.
And your process, should require a proper reference column in the approval table to the leave table. The linktoform should factor that into the formula, and prefill that column using the key value of the leave records. Thats only how dereferences will work. Worthy to mention, I dont see a related_approvals column in your posted image, which would always be created if you set up a reference properly