How do I know if/which trap/door/etc is linked to which lever?
Label them with a note N when constructed.
It's practically impossible to see what a lever operates without pulling it and seeing what happens.
You basically have a few options:
- Place the lever near the thing it affects (not great if you're wanting to consolidate levers to one control room with a stressed-out, twitchy dwarf).
- Color-code the levers by making them out of materials that have known colors.
- Color-code the wall behind or floor around a lever with a specific colored rock.
- Use specific colored rock to create a floor mosaic with letter(s) to label the lever.
- Organize your levers into bays (one alcove has door levers, another has traps).
- Any combination of the above.