Formula Variables and Reference Formulas

Feature Request: Formula Variables and Cross-BOE Formula References

Summary:
Enable users to treat existing calculations as reusable variables within the same BOE and to reference formulas from other BOEs. This will allow complex logic to be composed from smaller, validated components instead of duplicating logic in multiple places.

Problem Statement:
Today, each formula in a BOE must independently define all of its logic, even when that logic already exists elsewhere in the same BOE or in another BOE. This leads to duplicated calculations, increased risk of inconsistencies, and extra maintenance effort whenever a shared rule or rate changes. Users must manually keep related formulas synchronized, which is error-prone and makes complex BOEs difficult to manage and audit.

Proposed Solution:
Allow users to define formulas in a BOE that can be referenced as named variables by other formulas within the same BOE.
Provide a way to reference formulas from other BOEs (e.g., by selecting a BOE and choosing from its exposed formulas) and use their results as inputs in the current BOE’s calculations.
Ensure references are type- and scope-aware (e.g., only valid/compatible formula outputs can be referenced) and clearly indicate when a formula depends on other formulas or BOEs.
Handle dependency ordering automatically so that referenced formulas are evaluated before dependent ones, and surface clear errors if a reference is missing, circular, or invalid.
Optionally allow users to control whether a formula is “internal-only” or “exposed” for cross-BOE reference, to avoid clutter and unintended dependencies.

Benefits:
Reduces duplication by enabling reuse of common calculations across formulas and BOEs.
Improves accuracy and consistency, since shared logic is defined and updated in a single place.
Simplifies maintenance and change management for complex pricing or cost models.
Enhances transparency and auditability by making formula dependencies explicit.
Speeds up modeling and scenario-building, allowing users to assemble complex logic from a library of validated formula components.