Structure' s arrayfield manipulation

Hello everyone.
I need to call some external function of a dynamic library written in Rust using Declare statement. My Rust function has struct as parameter.
I have created a Structure, having a field named tasks(31) As StructureClass.
StructureClass is also a Structure having fields Strings, Integers, UInt64. Nothing Special.
I’ ve found in Xojo Docs related to Structure, that array fields cannot be manipulated like ordinary arrays. That makes sense to me, since a Structure is a limited space allocated in memory.
I was trying to set tasks(i) values as StructureTask with no success. How can I achieve that?
What are those “other ways” not specified in the Xojo manual?