How can I summarize a list of unused names?

Question

How can I indicate and eliminate names that are not shown on a chart here (see img att) based on a mass list of names on a separate spreadsheet?

Gill K · Accepted Answer

Hi Monchi,  thanks for sharing that sheet.  
And sorry, without a sheet to test it on, I had an error in my formula.  You can try this:
=SORT(UNIQUE(FILTER(FLATTEN(C7:U91),
                    FLATTEN(C7:U91) <>"")))
Then I think you now have to type in some sample names, in Main Chart, and put them on the same rows as in your real sheet.
You don't need to do too many, maybe ten or so, spread around the chart, just like in your real sheet.

Gill K · Accepted Answer

Hi Monchi,
Yes, I think that with a few formulas we can filter the list of mass names, to report only the names that are not already on the chart, if that is what you are trying to do.
This would be much easier, if you shared a sample sheet, with dummy names.  Please take a look at this post about Best Practices When Asking a Question and share a sample sheet that has the permissions set for “Anyone with link” can EDIT?  This will also guide you in avoiding sharing any sensitive data.  
Or this blank sheet maker​​​​​​​ can create a shareable sheet for you - just add your sample data.
But the approach would be roughly something like the following:
=SORT(UNIQUE(FLATTEN(FILTER(C7:U91,C7:U91<>""))))
That would collect the list of used names in the chart.  
We would then use a COUNTIF to compare that list against the names in your master list, and filter the master list to just the names that weren't produced from the first formula.
But you also have lots of hidden rows in your chart.  Depending on what is in them could affect the process.
And are you manually entering the names in the chart, or are they produced by formulas?
Cheers!
Gill