The advanced edit mode is an alternate building mode for Condo that you can toggle by using the Condo Inventory (button in the top left) or tilde key (~). It is intended to function similarly to map editing programs; while in advanced edit mode, you're always in no-clip mode and your inventory is always on screen. You can look around by holding right click, and move up and down by pressing E and Q respectively. The Tower Glove is unusable in this mode.
You can also toggle an option to edit surfaces while in advanced edit mode by left clicking on them, which is also in the inventory.