The documentation doesn't cover examples of using the dynamic nature of JavaScript only that you create observables with JavaScript objects with predefined properties:
1.
this
.set(
"current"
, items.get(itemID));
Specifically, the code above is a concern, because it gets "randomly" introduced instead of being properly declared as part of the object. So, if a team member were to be debugging code looking for the source of a problem related the property Current, they'd have a hard time because they wouldn't find it declared on the actual observable object.
Thanks for the link to the documentation. It was pretty much the standard stuff, I thought you may have been alluding to some pattern or practice that we weren't aware of.