It is customary for big templates with a lot of parameters, such as infoboxes, to have each parameter written on a separate line in the wiki source code.
If I am not mistaken, VE inserts all templates in one long line.
As long as source code editing is common, VE should insert templates according to the above community practice.
How to know whether to insert one line or multiple lines? Either do it with multiple lines if there are more than x parameters, say 4, or have a parameter in template data that suggests multiline insertion.