Sure you can get these information, related docs: http://devcenter.bitrise.io/faq/available-environment-variables/
I’d suggest you to check the Insert variables option:
In the Workflow Editor on bitrise.io you can click into any input field of a Step and a green Insert Variable button will appear.
Click this button and you’ll get a full list of available Environment Variables. You can search in this list, and when you find the one you’re looking for just click it, and it’ll be inserted into the input field for you.
This is an interactive list, which includes Environment Variables generated by previous Steps! This means, that if you click into an input of the third Step of your Workflow, the list will include all the Environment Variables (outputs) generated by the first and second Steps, but not the ones which will be generated by the forth, fifth, … Steps.