Has anyone condensed an QBD Enterprise DB that uses Bill.com?

I know how condensing your large file can help you do your future tasks in QuickBooks Desktop, @breanabb 

However, you need to know that condensing files is not reversible and can't be undone at a later point. Here are some valid reasons to condense:
 

• You have a large data file.
• You are nearing a list limit.
• You have upgraded all your hardware.
• Your accountant and your technical support have discussed other options and are willing to proceed with Condensing.

Also, it can possibly mess up your company's data and condensing may not fix the file damage. Below are the scenarios you might encounter:
 

• It most often reduces the size because it removes transaction details and list entries.
• If you use inventory items, your lists are not reduced. Very few transactions may be Condensed and the file size doesn't change much.
• Open transactions are not Condensed and the file size is not affected.
• It also affects various reports.

Moreover, if you still want to condense your file despite the possible risks. Below are the steps on how to:
 

1. In your QBDT file, go to the File menu, select Utilities, and then Condense Data.
2. Select the first option as shown below.  Note that the system will advise you of the approximate reduction in your file.
3. Select Next and the notice Working on your file now will appear. When complete, a window opens advising you of the total reduction in your file size as well as the location of the backup prior to the file optimization.

For detailed information, kindly visit: Use the Condense Data utility.
 

Additionally, I'll share this article you can use if you encounter a message when attempting to import your QBDT data to QuickBooks Online: Condense your QuickBooks Desktop file for import to QuickBooks Online.
 

I'm always around and ready to assist you anytime you have additional QuickBooks-related questions. Just notify me by leaving a comment below. Keep safe.

@breanabb 

But, I was told that it might not sync with Bill.com if I do that. Bill.com's support team will not assist and when I contacted QB tech support they also declined involvement. 

The real intention of the person who told you that was simply to avoid providing any help. If your QBD file is corrupted, they also simply refuse to help. I would recommend condensing your file and not bothering to tell Support if you use the condensed file when contacting them in the future.