For example: you want to copy a complicated conversion type that you have in one parameter from a layer, to other parameter (maybe not a root parameter, but a sub-parameter) of other layer. If you export the complicated conversion type from the original layer and then go to the other layer and select Connect (right click and the exported and the parameter both selected) then you have the parameter form the second layer to be exactly the same than the original one. But there is a drawback: if you modify one of the sub-parameters in the complicated conversion type (e.g. you change the value of one of them) then automatically the same sub-parameter of the other layer is changed.