Use flow variables

Flow variables pass named values — strings, integers, doubles, arrays, or paths — between nodes at runtime. Use them to change a node's settings without editing the node itself: for example, to parameterise a file path, filter value, or model threshold.

Choose how to create a flow variable

Pick the creation method that fits your situation:

If you want to…	Use
Drive settings from a lookup table	Table Row to Variable node
Export a setting from an existing node	Flow variable icon in the node's configuration dialog
Let users set the value interactively	Configuration or Widget node in a component
Create a variable with a fixed value	Variable Creator node
Compute a variable from other variables or expressions	Variable Expression node

Create a flow variable from a table row

The Table Row to Variable node reads the first row of a table and creates one flow variable per column. The column name becomes the variable name; the cell value becomes the variable value. Additional rows are discarded.

This is the right choice when configuration data lives in a table — for example, a parameters sheet loaded from a file.

Export a node configuration as a flow variable

1. Open the configuration dialog of the node whose setting you want to export.
2. Click the flow variable icon next to the field.
3. Enter a name in the Output as flow variable field.

The variable is available at the output flow variable port of that node from the next execution onwards.

Pass flow variables to downstream nodes

Every node has flow variable ports - the small red circles above it, visible on hover. Connect the output flow variable port of one node to the input flow variable port of another. You only need this explicit connection when the two nodes share no other port connection.

Once connected, all variables flowing through that port are available to every downstream node in the chain.

Overwrite a node setting with a flow variable

1. Open the configuration dialog of the node you want to control.
2. Click the flow variable icon next to the setting.
3. Select the variable from the dropdown.

Only flow variables compatible with the setting's type appear in the list — a flow variable of type String, for example, doesn't appear when replacing a value of type Integer.

Once a setting is overwritten, the field becomes unchangeable in the configuration dialog. It shows the flow variable's value if that value is already known; otherwise, it shows a placeholder or fallback value until the variable is resolved during execution.

Use flow variables in loops

The Table Row to Variable Loop Start node combines table-to-variable conversion with looping: it iterates over the input table row by row, exposing each row as a set of flow variables for that iteration.

See Loops and workflow control for all loop node types and branching options.

Use flow variables in expressions

Expression-based nodes such as Expression and Variable Expression support flow variables in their expression syntax, using $$["flow var name"] or $$flow_var_name.

See the expression language reference for the full syntax.

Widget and Configuration nodes

Widget and Configuration nodes create interactive dialogs for the user, respectively for component composite views and component configuration dialogs. The value inserted by the user is then output as a flow variable usable within the workflow.

See the component guide for more information about widget and configuration nodes.