I've never really cared what my job title was (though in retrospect now that I'm looking for another job I should have been). Anyway, I was a "staff engineer" for many years. A couple months before the company I work at was acquired by another company I was "promoted" to "senior engineer". The promotion was in name only. I do the exact same job for the exact same pay, they just changed my title. I didn't know the company was going to be sold at the time, but now I think the reason for the title change was so that I entered the new company as senior engineer instead of staff engineer. The new company gave me a manager title instead of an engineer title, along with some new responsibilities and a nice pay cut. The new company also promised year end bonuses (which I received 12 out of 12 years at the old company) and then boned the entire region by not paying out any bonuses. We've had 2 people jump ship already, and me and a couple others are not far behind.
How do I reflect that on my resume? I feel like listing senior engineer for my entire tenure is disingenuous. However I feel stupid creating another heading and only listing it for 2-3 months. I've been gradually gaining new responsibilities during my entire career, so I could conceivably list the senior engineer title, say I maintained all the responsibilities as staff engineer, and create a few new bullet points. I could also just as easily list those bullet points under the staff engineer.
How should I handle this on my resume?