First, to address the functionality in question:
The main text field in the Text Exporter (i.e. the one that is not "Header text" or "Footer text", executes once per selected Contact Sheet item, and it will *always* move to a new line for each Contact Sheet item.
The "Replace carriage Returns & Line Feeds with Single Space (Excel friendly)" checkbox refers to how it formats the input for output, not the formatting of the output itself. For example, if I am exporting the captions of the images into a text file using the text exporter, with "{caption}" in the main field, and I had an image with the caption:
This is a two
line caption
The result from the export with that box checked would be:
"This is a two line caption".
Given that the text exporter doesn't currently do what you want it to do, I would recommend opening the file that Photo Mechanic created in some spreadsheet software, and then you can rotate the column into a row and then export that as a text file. (There's probably other ways to do this in just a text editor, but that's the first thing I came up with)
I guess my disappointment is largely routed in the fact that you used to have an excellent manual -- back in the days of Pm4 and 5. But that manual has been replaced. Now I grant that the new design is much cleaner and prettier. But it has been dumbed down to the extent that, in my view, it largely useless .....
The manual Photo Mechanic v5 documentation/wiki still exists at
https://wiki.camerabits.com, but as it turns out, that manual also doesn't come close to answering your question. So it's not a case of formatting or attempting to dumb it down from the old version. It's simply an omission that we didn't realize was omitted. Now that we know that it was omitted, we can work to improve it.