Look for opportunities to take on roles if there is volatility. I moved into management when our current manager left and I volunteered to be an interim manager. I did well and they moved me into the position permanently. You may want to consider changing jobs. If current management does not see you as management material, it may be that you’ve been there too long. It’s very difficult to change people’s perception of you rather than creating a new first impression.
Dress for the position you want. Perception is (almost) everything. Dress like the managers do (if they dress nicer than everyone else). In general, dress just a little bit nicer than everyone else. If everyone wears t-shirts, wear a collared shirt. If everyone wears collared shirts, wear a blazer. If you look like manager but aren’t, people will ask whether you’re a manager. You’re halfway there if people suspect you’re a manager. If you don’t look like a manager, people won’t see you as a manager, both literally and figuratively.
Act like a manager by always following up on items, especially with your managers. Don’t let anything fall through the cracks. Your manager should never, ever have to check back with you on something they asked you to look into. Even if it can’t be done, make sure that you’re the one that follows up on it with them. Follow-up with coworkers on items you’ve asked them to do. Don’t be afraid to pester people. Send emails asking, “Any update on this?” Find a way to track all these things. Keeping track and following up is critical. Record and transcribe meetings with supervisors to make sure nothing falls through the cracks.
Improve your social skills. Learn public speaking if necessary so that you can sound confident in front of people.