The Join and Normalize operation is only available in the editor. There is no batch counterpart.
However, you could use the Find/Replace in Files tool from Oxygen to do the same on multiple files. I recommend creating a backup copy of the files before performing this operation on them.
Because of the nature of the Find/Replace in Files tool (limited to matches on the same line up to v13.2) you will have to perform this replace operation twice.
Text to find: '\s+' (without the quotes)
Enable Regular expression.
Replace with: ' ' (a space character without the quotes).
Make sure the correct Scope is selected and that the Include files filter covers your files. Recurse subdirectories should also be enabled if you want to search deep in directories.