Want to add new data to my recently submitted paper I recently submitted my manuscript to Journal of optics (IOP Publishing). Unfortunately,I noticed that I forgot to add one specific figure to the paper. The general quality of the manuscript is good. I was wondering if I would be able to add that figure maybe in the revision process. Do you think reviewers suggest a major revision or a minor one, or maybe a reject and resubmit? The exact question is that to what extent one can modify his/her manuscript while it is considered a minor change and hopefully an acceptance? (Is just adding a figure a big change?) 
Thank you for your time and consideration.
As long as your paper is under revision, you can improve things.  Those improvements are not limited to those suggested by the reviewers, however:


The improvements should not change the nature of the paper too much, or you will annoy editor and reviewers.  Make sure they haven't wasted their time by reading the first edition.
Make clear that you have made this addition.  Some reviewers may only look at alterations based on their own recommendations, rather than re-reading the whole paper from start to end.


Once your paper is accepted, you can no longer add new data, text, or figures.