[BetterRed]

I think the OP knows why the '_' (underscore) character is substituted for disallowed characters (e.g. <>:"/\|?*) in file names.

What they want to do is to use another substitute character in Save to Disk, Send to Device templates and plugboards etc. Or even better a substitute string e.g. ' — '.

Personally, I would get rid of the ':' in the Title when I added the book, either via use of a subtitle column or by changing the ':' to ' — '. But that wouldn't suit everyone.

BR