I recently removed some shelving from the greenhouse to grow tomatoes in pots over winter. Worked out great but meant less space for seedlings.
We have capsicum from last year which was cut right back and only just sprouting. I noticed there was a lot of unused space around them so I cut some wood to sit on the wooden frame and have now claimed that space.
Works out that I just have enough space to pot up all the seedlings.
I find these plastic stackable containers are great if you use bags for potting up. I drill holes in the sides about a cm from the bottom. That way I can dunk the whole tray to water them and then drain it. When it's hot, the cm at the bottom allows me to keep a bit more water in especially when they are really thirsty.