Escape Sequence \n can be used to add new line in Long Text Area field using Apex in Salesforce.

Sample Text Area Long Field:

Sample Code:

trigger AccountTrigger on Account ( before update ) {

    for ( Account objAcc : trigger.new ) {
    
        Account objAccWithPriorValues = trigger.oldMap.get( objAcc.Id );
        
        if ( objAcc.Type != objAccWithPriorValues.Type ) {
            
            String strTypeTrackValue = 'Type value is changed from ' +
                    objAccWithPriorValues.Type + ' to ' + objAcc.Type + 
                    ' on ' + System.now();
        
            if ( String.isBlank( objAcc.Type_Change_Tracking__c ) ) {
                
                objAcc.Type_Change_Tracking__c = strTypeTrackValue;
                
            } else {
                
                objAcc.Type_Change_Tracking__c += '\n' + strTypeTrackValue;
                
            }
        
        }
    
    }

}

Output: