The Process builder formulas don't support new line character. Some websites suggest using BR(), but that results in something like this:

Instead, we can create a Custom Label in our org and use it in our formulas. 

Let’s start with a business use case

Business Use case :-  Pamela Kline is working as System administrator in Universal Container. She wants to update the Lead’s Description field with Lead Name, Lead’s Last Name in the next line of Lead’s First Name.

Solution for the above business requirement

One workaround I’ve found is to use Custom label and SUBSTITUTE function in process builder formula. Follow the below instructions to create a Process Builder and Custom Label to solve the above business requirement

1. click on  Setup | Build | Create | Custom Labels 
2. Click on New Custom Labels, it will open the new window for you. Now create a new custom label, as shown in the following screenshot

Custom Label


3. To create a new Process, click on Name | Setup | App Setup | Create | Workflows & Approvals | Process Builder  and click on the New button, Enter NameAPI Nameand then click on the Save button.
4. To create a new process from scratch, click on the New Button available on Process management page. A popup will appear, where you have to enter the Name (Use Line break in Process Builder formula as name)API Name and Description as shown in the below screenshot.

Define Process Properties


5. Click on Object node to add object and then select Lead object. For the entry criteria, Select when a record is created or edited, as shown in the below screenshot 

Evaluation Criteria


4. The next task is to add Process Criteria, To do this click on Add Criteria, enterNameType of action and set filter conditions  (In this case select No Criteria – Just execute the actions!and click on the Save button as shown in the following screenshot

Process Criteria


5. The next step is to add an Immediate action to Process. Click on Add Action(Under Immediate actions), Select the type of action to create (In our case Record Updates), and then fill the values into fields to define the action, as shown in the following screenshot.

Add Action - Update Records


Where $Label.NewLine represents the custom label

6. Once you are done, click on the Save button, it will redirect you to Process canvas. Finally the Process will look like the following screenshot

Line break in Process Builder formula

Don’t forget to active the Process by clicking on the Activate button.

Proof of concept

Lead Record