Going into Q4 there seems to be a lack of projects allocated from planning to our team. I think this is related to our manager being on parental leave last quarter and not having an advocate at the higher level planning meetings.
My question is also around how to deal with a situation where projects are strictly determined from the top-down (aside from engineering/maintenance + backlog issues, which are less valued).
A trait of a senior engineer is being able to define work for themselves. It doesn't have to be (and probably shouldn't be, in your case as a mid-level engineer) some multi-month effort that requires lots of buy-in. Some ideas:
If you're on a team where this is impossible, it's going to be much harder to grow. You want to be in a company where there are more problems than there are people. Problems create opportunities for growth.
I agree with Rahul here. When I was working in Facebook (2011-2017), there was a lot of growth, but even with that, some projects in backend engineers "seemed to dry up", especially when people were busy fighting fires. Good engineers tended to dig into the fires and operational work and find the patters and root cause them. And define work for themselves. I have seen many promotions with such projects.
Define your own work.