Hey, UiPath (VB.Net expression editor) do support multi-line code. This can be achieved using a line-continuation character (not aware of the technical name, though!).
As Microsoft document states,
Use the line-continuation character, which is an underscore (
_), at the point at which you want the line to break. The underscore must be immediately preceded by a space and immediately followed by a line terminator (carriage return).
Example with the Assign activity:
Hope this helps :)))