You are also able to create custom exercises via the JEFIT Website from your My-JEFIT Profile Page
Once you have logged in your My-JEFIT Account, you will click the "My Custom Exercises" button on the left panel underneath your profile picture.
By clicking on this button you will be taken your Custom Exercises page of all of the custom exercises that you have created/stored within your account.
There will be a table at the top of the page labeled "Create Custom Exercise", which will allow you to create the custom exercises that currently aren't within the built in exercise database.
Upon completing the creation of your custom exercise you will click create exercise and this will create the custom exercise within your own personal database.
You can send these exercises to your application by opening up the JEFIT Application and clicking "Sync" which will send the exercises to the custom exercise database within your app.