Cleaning up Jira cloud

[Kimi Nakashima]

I have recently been tasked with being the main admin for my employer's Jira service desk cloud. I have never worked with Jira before and there was a lot of work done (and deleted) in it before I got my hands on it. So what I inherited was a lot of screens, workflows, schemes, etc.  I've managed to get rid of most of the workflows, screens, and issue types that were connected to deleted projects and I want to tackle the custom fields. But there are so many fields and I'm having a difficult time figuring out which ones were default fields created by now deleted projects, which ones were created for now deleted projects and which ones were created but never used. 

I'm hoping that there is a way to simplify what's looking like a very tedious cleaning project. I'm also hoping that there is a way to do it without an add-on (although I'm not holding my breath).