A parameter is a named value with a unit, such as max_mass = 12 kg, defined on one item and referenced from the text of others. When the value changes, every reference shows the new value and is flagged so you can check the requirements that depend on it. Parameters are marked Beta in the left sidebar.
Where parameters live
A parameter is an attribute of parameter type on an item. Add one from the item details sidebar with + and pick the parameter type, or create it in the editor while linking, as described below. The parameter's name is the attribute name; its value and unit are the attribute's value.
The parameters page
Click Parameters in the left sidebar. The page lists every parameter in the organization with the columns Name, Value, Unit, Defined in, Used by, Created and Last updated. Type in the search box to filter by name. The filter button offers Include deleted parameters and Include deleted items.
Defined in shows the item that holds the parameter; hover for a preview or click to open it in single item view.
Used by counts the items whose text references the parameter. Hover it to list them. A warning icon means a reference is suspect because the value changed after it was inserted, or the parameter was deleted.
Referencing a parameter in text
In any text attribute, type $ followed by the parameter name, or type / and choose Link a parameter. The Link parameter? popover lists matching parameters with their values and the items they are defined in; click one to insert a live reference showing its value and unit. To create one instead, click New parameter at the bottom of the popover, enter a Name, Value and Unit, and the parameter is created on the current item and inserted in one step.
With Parameter suggestions turned on in the view settings, the editor also underlines numbers with units in your text and offers to link or create a parameter for them.
When a value changes
Hover a parameter reference to see its name, value, unit and the item it is defined in. If the value has changed since the reference was inserted, the reference is badged and the popover reads Parameter value change, showing the old and new value; click Clear suspect once you have checked the text still holds. If the parameter was deleted, the popover reads Parameter deleted and lets you convert the reference to plain text or create a new parameter in its place.
Parameters and baselines
Baselines can pin parameters alongside items, so a frozen baseline keeps the parameter values it was created with. This is done through the API; see Creating baselines.