How to exclude docker files from time machine backups
I use the generic addexclusion clause of tmutil to make files not get backed up even if I move or copy them.
Open a Finder window to the files and a command line prompt (terminal.app is fine for this) and drag that file into the prompt after typing tmutil addexclusion and press enter. Here you can see me checking files on the desktop of a user named mike...
mike@m1 ~ % tmutil isexcluded /Users/mike/Desktop/Docker\ Files 
[Included]    /System/Volumes/Data/Users/mike/Desktop/Docker Files
mike@m1 ~ % tmutil addexclusion /Users/mike/Desktop/Docker\ Files 
mike@m1 ~ % tmutil isexcluded /Users/mike/Desktop/Docker\ Files   
[Excluded]    /System/Volumes/Data/Users/mike/Desktop/Docker Files