This feature is avaliable in SP695+. 
If you already have OpenVPN configured before the upgrade, you must create a new CA certificate and reconfigure the OpenVPN service and rebuild all the client scripts. 
 
 
 
On left menu select OpenVPN  
Parameters  
Select the new certificate  to be used by the OpenVPN service 
On the bottom of the page click Apply  and then Reconfigure Service  
 
 
On left menu select OpenVPN  
Client Scripts  
Click on the botton Create a new connection  
Set the connection name  
On operating system dropdown  select Linux  
Click on botton Generate parameters  
 
 
After you create the script, click on the button Build the script  or Run  
 
 
After you build the script, click on the button Download  
 
 
On pfSense, go to System / Certificate Manager 
On CAs  tab, click on the botton Add  
 
Set the Descriptive name  
On Method  dropdown, select Import an existing Certificate Authority  
Check the option Trust Store  
 
Open with notepad or other IDE the OpenVPN client script previously downloaded. 
Copy the key inside < ca >  tag and paste it inside Certificate data  textarea. 
 
 
Click Save  
 
On pfSense, go to System / Certificate Manager 
On Certificates  tab, click on the botton Add/Sign  
 
On Method  dropdown, select Import an existing Certificate  
Set the Descriptive name  
In Certificate Type , select X.509 (PEM)  
 
Open with notepad or other IDE the OpenVPN client script previously downloaded. 
Copy the key inside  < cert >  tag and paste it inside Certificate data  textarea. 
 
 
Copy the key inside  < key >  tag and paste it inside Private key data  textarea. 
 
 
Click Save  
 
On pfSense, go to VPN / OpenVPN  
Select Clients  
Add  
 
In Server Mode  select Peer to Peer (TLS/SSL)  
Set the Protocol  configured on OpenVPN server, by default is UDP  
Set the Device Mode  configured on OpenVPN server, by default is Tun  
Select the outgoing Interface  to be used by the OpenVPN client. 
Set the Server host or address  of OpenVPN Server 
Set the Server Port  of OpenVPN Server 
 
If you enable authentication on OpenVPN server, set the username and password 
 
Uncheck the option Use a TLS Key  
In Peer Certificate Authority  select the CA certificate. 
In Client Certificate  select the client certificate. 
Allow AES-256-GCM, AES-128-GCM and CHACHA20-POLY1307 in Data Encryption Algorithms  
Save 
 
 
On left menu select OpenVPN  
Sessions  
 
 
On menu Status , select OpenVPN