In Tableau Desktop, when creating a parameter based on a boolean output it will automatically offer the ability to add a true and false outcome as shown here:
In Tableau Next, this is currently not possible and will only recognise a true value/condition and not a false:
To work around this we will change the parameter to work with numbers as the data type instead and use aliases to display true and false:
We will now construct our calculation to work with this new parameter when the condition is met, in this case to separate the years when it is selected as true and to unify them when false:
We drag this calculation on to our visual and change it to a dimension
From here we will create a new dashboard to test the parameter action works: Drag in a visual object and select the visual that has been created and drag a list object in for our parameter:
To test the parameter we click on the preview button in the top right
We can see the default "true" value is working as each year is separated out:
To change the value, click on the drop down to display the list of options, click the false option and then click "Done" to apply your choice and the visual should dynamically change and show "All Years":
And that is currently the best way (so far) to make boolean parameters work in Tableau Next! Prior to the numbers data type being used, the string data type was tested but it also failed when used in the calculation. Hopefully in a future update boolean parameters will work as intended.