why no search of subfolders when using "search missing files" feature ?

Because your task is to locate that file itself, not a folder.

thanks a lot for that profound answer.

rekordbox uses the base location of the first file it's searching for as the path for all other moved files. rekordbox itself isn't searching for the file, YOU are because chances are YOU moved it.

i understand how rekordbox handles that situation.

will there be an update fixing that problem?

or better sayed, do you consider adding searching on a more global

level in a future update ?

Not sure what you mean? 

When relocating my entire library to another drive I selected all, clicked relocate on a file while they were all selected, found it. Then it asks you if you want to find the rest and it searched and found all of the files that were missing in all of the many folders and sub folders.

@Steffen > It's not a problem; if you moved a file (or files), then the process is to select ALL of your files, then use the relocate missing files feature, locate the FIRST file it asks for, and provided you moved all of your music in the same scope (eg. put the entire set of music files into a new folder called "New"), it will automatically relocate the entire batch.