When you reference a declaration in the library from other logic such as a service or handler, you can include the library name as a prefix. For example, MyLibrary.myLibraryVariable is appropriate if the library name is MyLibrary and the library includes the myLibraryVariable variable. Alternatively, you can include the library name in a use statement in the other logic and avoid the need to qualify every reference. In that case, myLibraryVariable is sufficient to reference that variable.
To create a Library part:
categories STRING[] = [
"Rent", // 1
"Food", // 2
"Entertainment", // 3
"Automotive", // 4
"Utilities", // 5
"Clothes", // 6
"Other" // 7
];
The value is an array, and as is true of all arrays in EGL, the index of the first element is 1, not 0.