Linked constraints don't work with spaces.

[chrisb]

...so maybe I am working on Expressions

That would be highly appreciated!

[adrianinsaval]

If it is forbidden in expression it should be forbidden in labels too IMO, or the users will constantly find that the labels they assigned are useless, and working with the real names of features is really unintuitive. I would prefer if it was allowed using the <<label with space>> sintax but if it is too much trouble I guess it's not worth it

[chrisb]

I would prefer if it was allowed using the <<label with space>> sintax but if it is too much trouble I guess it's not worth it

And that will raise issues in other places, e.g. if you use labels such as
>>rightmost object or <<leftmost object.

In my experience there are rather few labels used in expressions. And renaming some labels is not such a big deal. In your case it may even be appreciated: you see immediately which items are used in expressions.