Moving the file worked; the problem was on my end.  Sorry!

I currently use Firefox, Brave and Safari without syncing the data between browsers or devices i.e. I'm using BookMacster directly.

I want to move a single URL collection from my Dropbox folder to my Documents folder.  (I plan to quit using Dropbox in favor of iCloud and other more secure options.)

I have read the pertinent sections of BookMacster Help but I haven't been able to figure it out on my own.  Using the Finder to manually moving the data file has not been successful and I cannot locate info for performing this action within BookMacster.