You should use the same title all the way through your GC applic

What I mean is that you should use the same title when you apply PERM, I-140 and I-485. You should accept your promotion. It will not affect your GC application as long as the same title (the one you used for your PERM application) will be used in PERM, I-140 and I-485. For my case, I used Software Engineer as my title when I applied PERM even though my real title was Sr. Software Engineer then. Later on, when I applied I-140 & 485, I used the same title. By the way, Department of Labor classifies Software Engineer without using “Senior”. Instead, it uses Software Engineer I, II, III, IV and V.