According to my experience, you already can do it. The only condition is that those segment have to be in the same paragraph. You can merge more than 2 segments even if they are separated by a full stop (which is the basic segment parsing criteria), but not if there is a carriage return (the end of a paragraph, which can be inadvertently inserted – mainly in PDF documents) in between, because, unlike a full stop, a carriage return relates to the actual structure of the document, and Studio is not intended to change that.

According to my experience, you already can do it. The only condition is that those segment have to be in the same paragraph. You can merge more than 2 segments even if they are separated by a full stop (which is the basic segment parsing criteria), but not if there is a carriage return (the end of a paragraph, which can be inadvertently inserted – mainly in PDF documents) in between, because, unlike a full stop, a carriage return relates to the actual structure of the document, and Studio is not intended to change that.