I added materials to all the geometry surfaces in level 5, and scattered a few gold pickups. Then I started on level 7.
I kept it fairly short and mostly blueprints again, which made me realise how hard it was going to be to design all the levels I needed without a plan, so I decided that from here on out I would make a plan map for all the levels before I started actually making them.
I made a quick map of the next level:
I quickly blocked it out using geometry, then worked out a way to complete the level using blueprints. For the end, I decided to use an old technique from college: a gate that blocks progression, that can be raised using a key from within the level. It's a bit of an odd one that requires getting a reference to an object from within the level in the level blueprint, as opposed to having all the functions for that object contained within its own blueprint, but it works very nicely.
I watched some tutorials to refresh my memory, but it was taking a long time to find something that worked the way I wanted it to, so I gave up for the night.