Multiple Business accounts with the same email+2 Business accounts on the desktop.

IanSp 

Create a folder such as C:\DB then C:\User1 C:\User2 C:\User3

(replace User? with the names of the accounts or email or whatever you want)

Login to each user profile and move the dropbox folders to said matching user C:\DB\User? So it's like C:\DB\User?\Dropbox (blah blah)

Return to your primary profile, and assign full file access to it in C:\DB. 

(not always needed but sometimes access permissions are missing)

On your primary profile desktop right-click and select a NEW shortcut, enter

C:\Windows\System32\runas.exe /savecred /user:USER2 "C:\Program Files (x86)\Dropbox\Client\Dropbox.exe" 

Run the Shortcut and enter the username and password for USER2 (one-off action)

Repeat again for USER3, 

(USER? is the user profile names of User2 and User3 I'm assuming that the primary profile is USER1 here, if not make 3 shortcuts and do USER1 as well)

Optionally copy these to shortcuts to the startup group.

All 3 Dropbox will now start within the primary profile.

* see you need a profile for each dropbox, but you don't need to load the profile to run the dropbox application. RUNAS.EXE will run the application in the right security context of the profile mentioned in the /USER: switch, while the application runs in whatever profile you launch it in.

I run 2 DB's right now, I used to run 4. But have switched to OneDrive for better cloud co-authoring support. This method of multi-launch has worked with Dropbox for many years and should continue to do so forever since that is how windows works.