Fabulous Poloniex is a script giving you the ability to see the total amount of BTC gained on active loans in real time.
Requires either GreaseMonkey (FireFox) or Tampermonkey (Chrome, Opera, Safari, MSE).
You can use this YouTube video or Google installing userscripts.
Once you have it installed. Go to your lending page and take a look below "My Active Loans". You should see something looking like this:
Let me deliver you better content by dropping me a few tokens of appreciation.
BTC Addy: 18rQ5HzSwaFKvR54CCNhgq7eUDyN84X4Lu