> For the complete documentation index, see [llms.txt](https://help.modelreef.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.modelreef.io/syntax/formula-syntax/selecting-drivers-in-sidebar.md).

# Selecting Drivers in Sidebar

This article explains how to **select drivers from the Formula editor sidebar** in Model Reef.

You will learn:

* How drivers are grouped and displayed.
* How to insert drivers into formulas.
* How scenario specific drivers behave in the editor.

Drivers are reusable assumptions. Referencing them correctly makes your model easier to maintain.

## Driver groups in the sidebar

In the Formula editor sidebar, drivers are usually grouped by type:

* Economic drivers.
* Operational drivers.
* Modifier drivers.

Within each group, drivers are listed by name. Clear naming helps distinguish similar series.

## Inserting a driver into a formula

{% stepper %}
{% step %}

### Open the Formula editor

Open the Formula editor where you author expressions.
{% endstep %}

{% step %}

### Expand the relevant driver group

Expand the relevant driver group (economic, operational or modifier) in the sidebar.
{% endstep %}

{% step %}

### Insert the driver reference

Click the driver name. The reference is inserted at the cursor in the expression area, using the correct internal reference syntax.
{% endstep %}
{% endstepper %}

## Driver search and filtering

If the sidebar supports search:

* Type part of the driver name into the search box.
* The list filters to drivers whose names match.
* Click a result to insert it into the formula.

This is especially helpful in large models with many shared drivers.

## Scenario specific drivers

Each scenario is its own model, with its own drivers:

* The sidebar always shows drivers from the active scenario model.
* Editing a driver in one scenario does not affect others.
* Formulas referencing a driver remain valid within each scenario as long as the driver exists there.

This makes it easy to tune assumptions per scenario while retaining structural consistency.

## Using drivers instead of hard coded inputs

Using drivers instead of hard coded numbers in formulas:

* Centralises assumptions, so one change updates multiple series.
* Makes sensitivity analysis simpler.
* Improves transparency for reviewers who want to see where assumptions live.

Reserve hard coded numeric constants for true constants, not for assumptions that may change.

## Related articles

* [Selecting Variables in Sidebar](/syntax/formula-syntax/selecting-variables-in-sidebar.md)
* [Using Drivers in Formulas](/syntax/drivers-syntax/using-drivers-in-formulas.md)
* [Naming (Drivers)](/help/building-your-model/naming-drivers.md)
* [Build a Variance Analysis Model](/how-tos/dashboards-and-reporting/build-a-variance-analysis-model.md)