Switch Between Usernames in Lightning Experience

Note: Available in Lightning Experience ONLY

Start with adding your multiple accounts:

1. Click on your avatar.
2. Click Add Username under Options.

After clicking, you will be redirected to the login form of Salesforce where you have to enter the other account credentials that you wish to conveniently switch to.

Once you are on Salesforce Home, you'll be able to see the account you are logged into before you add the second account. 

The System Administrator of the organization can actually enable and disable this functionality if their users find this unnecessary. 

To enable or disable this feature, please see the following instructions:

1. Go to Setup.
2. Enter Session Settings in the Quick Find Box and click it from the results.
3. Select Enable user switching under Caching.
4. Click Save.