...
In the Formula Designer, click the Add > Add Type button to open the Edit Types dialog.
A draft “NewFormulaXX” is now created.
Optionally, you can import an existing Formula Type in the JSON format (Add > Import).Build the type using blocks by following instructions described in the Formula Designer for Technical Users article.
Once you have finished building and your formula type is valid (see the indicator next to the formula type’s title), activate the draft using the blue Activate button (top-right corner of the block editor).
Your formula type is now displayed among the Active types. If you want to apply the type to the formula, click the Use in Formula button.
...