Dozens of completely different .scr files exist, so it's actually difficult to give a specific answer for a particular conversion, especially when its from plain text format. Many .scr files are various scripts, so for these a good text editor is all you need to prepare new ones, but of course that requires knowledge of the particular syntax.
The first step how to achieve txt to scr conversion would be thus to determine what kind of .scr file you actually need and select program based on that.
Updated: August 29, 2023