Link to the 360 Page via the SFDC Account Page in Lightning

Gainsight support provided the following (which worked for our team):

Here are some more details regarding a Lightning URL. The parameters in a lightning URL are base64 encoded. Let's take the following Lightning URL as an example:
 

https://nearpod.lightning.force.com/one/one.app#eyJjb21wb25lbnREZWYiOiJvbmU6YWxvaGFQYWdlIiwiYXR0cmlidXRlcyI6eyJhZGRyZXNzIjoiaHR0cHM6Ly9uZWFycG9kLS1qYmN4bS52Zi5mb3JjZS5jb20vYXBleC9HYWluc2lnaHROWFQjY3VzdG9tZXJzdWNjZXNzMzYwJTNGY2lkJTNEMVAwMjUzR0NISU5XWjBLSU9aMjdBMlFDQkhYTTE5RVRJOVZFIn0sInN0YXRlIjp7fX0%3D

 
In this URL, the base URL is "https://nearpod.lightning.force.com/one/one.app". Everything following this (excluding the is the URL parameter, and it is base64 encoded.

If you decode the following encoded parameter value

eyJjb21wb25lbnREZWYiOiJvbmU6YWxvaGFQYWdlIiwiYXR0cmlidXRlcyI6eyJhZGRyZXNzIjoiaHR0cHM6Ly9uZWFycG9kLS1qYmN4bS52Zi5mb3JjZS5jb20vYXBleC9HYWluc2lnaHROWFQjY3VzdG9tZXJzdWNjZXNzMzYwJTNGY2lkJTNEMVAwMjUzR0NISU5XWjBLSU9aMjdBMlFDQkhYTTE5RVRJOVZFIn0sInN0YXRlIjp7fX0%3D

 
You would get the following json:

{"componentDef":"one:alohaPage","attributes":{"address":"https://nearpod--jbcxm.vf.force.com/apex/GainsightNXT#customersuccess360?cid=1P0253GCHINWZ0KIOZ27A2QCBHXM19ETI9VE"},"state":{}}

 
In this JSON, the "address" part represents the same address that you generated using the formula field.
 
To populate the Lightning URL into a text field in Salesforce using Apex, you can use the following sample code:

List<Account> lAccounts = [Select Id, Company_GSID__c, Name From Account limit 2000];
Map<Id,Account> AccountWithUrl = new Map<Id,Account>(lAccounts);
for(Account acc : lAccounts){
    String base = 'https://nearpod.lightning.force.com/one/one.app#';
    String pageJson = '{"componentDef":"one:alohaPage","attributes":{"address":"https://nearpod--jbcxm.vf.force.com/apex/GainsightNXT#customersuccess360%3Fcid%3D'+acc.Company_GSID__c+'"},"state":{}}';
    //Blob encoded = EncodingUtil.base64Encode(pageJson);
    acc.NewURLField__c = base + EncodingUtil.base64Encode(Blob.valueOf(pageJson));
    AccountWithUrl.put(acc.Id, acc);
}

update AccountWithUrl.values();

 
Please note that this is just a sample script to demonstrate how to create and update the URL. 
 

@gunjanm We try to keep our users within the Salesforce environment, and the above solution worked brilliantly!