You will not need to create a .lsb file. The recommended method of handling structs with strings with Call Library Function Node is as follows:
1. Use DSNewPtr, MoveBlock to allocate string in LabVIEW, copy contents into allocated space. These functions are accessible via Call Library Function Node, set library to LabVIEW.
2. Use Call Library Function Node to call function in C DLL. Pass cluster in, use Adapt to Type
and Pointers to Handles
3. Dispose of allocated string in LabVIEW with DSDisposePtr.
See the community forum discussion Solved: Passing Cluster Containing Strings in C DLL as Struct
for example code and further discussion.