Is there a way to see all Guru items?

I know two ways of doing this.

The first one is the Item Inspector script. It displays items in a table. You will have to add a table configured with the SRS level filter to make it do what you want.

The other method is to use wkstats. You go under Item then Wanikani and you can configure the report to sort items by SRS stages.

Both methods will work equally well, so it is up to you.