Rationale
The Export command is useful for creating emergency backups of your vault. Unfortunately, not all vault data is exported from the vault when you perform an Export command.
The Bitwarden Export documentation does a good job describing what information is NOT exported. However, you may not read the documentation 
and erroneously think that all data was exported by the Export command. A warning message should be added when you use Export to make it absolutely clear what is NOT exported.
Implementation Details
A warning message should be added to all the web, desktop, and browser extension user interfaces. The following is the Export screen for the web interface:
This screen should contain something like the following near the bottom:
Warning: Vault exports will not include file attachments, items in the trash, password history, or Sends.
CVS files export even less data than JSON files, so the message for CVS files would have to be modified as follows:
Warning: Vault exports will not include file attachments, items in the trash, password history, Sends, cards or identities.
