dnd 5e – Are there guidelines to create new spells / magic items and find their level / rarity when it does not cause damage / does not have an equivalent spell?

As far as I know, the rules in the dmg only describe spell levels for spells that involve damage, in their table. For magical items that do not follow spells, such as a ladder that can expand or compress down, that do not act in a similar way to spells, is there a way to find the rarity / equivalent spell level? I will allow content outside the main books to be used in the response. I also want