Hello,
I know there is a way to see what custom check boxes have been used already in developer mode, but I can’t remember how to get there? I want to use unused check boxes and character fields but it can be cumbersome to figure out which ones are free by creating BAQs and pulling in those fields.
It’s been a while since using E9. I think your BAQ suggestion or a sql query on the specific table is all you have, then you can eyeball the results…provided the fields actually have data you can assume they are being used for something.
Whilst my next comment may not be that helpful. May I suggest, going forward, keeping a log of the use of the custom fields, that way there is no need for the BAQ/SQL. Not to mention if you get hit by a bus the next person has something to go on, 
Yea, the issue we have is that the last person who took care of all of our customizations left, so I’m now assisting. He did show me in one view how to see all of the fields, so I know it is possible, I just don’t remember how to get there!
He may have had some prebuild BAQs so you could look at BAQ designer and search there. They may have created some views in SQL so you could run a select statement in SQL Management Studio (SSMS).
That is of course your version is the SQL version of E9, if it is the straight progress database then there may be some other way, but I’ve never had the privilege to work with the a straight up progress version of E9…so perhaps someone else may have an idea… Any Vantage veterans kicking around?
Here is my method: I search for BAQs then right-click copy to Excel. I name the worksheet BAQs. I do the same with Dashboards in another worksheet called Dashboards. In the BAQ worksheet, I have columns: Used on (which dashboard(s)), and Menu if it’s been added to a menu.
Too bad there isn’t a comment field in BAQs and a date/time stamp. And I agree with Hally - about getting hit by a bus. I hope that doesn’t happen!