Currently, we don't have a better option other than use a simple division. We plan to better support the unit in Visual Scripting in future, as Length is one of the datatype we support. It should be converted between different display units automatically, as the internal value of them are the same under a same physical length...

Personally, I don't really like the idea about a constant node "1000", as "1000mm → 1m" is just one conversion. "10mm → 1cm" is already another one. It gets more complicated, if we need to support conversion between imperial unit to metric unit by having dozens of different constant node.