Ok martin, I hope this flexibility be added in feature.. It's not a useless one. I'm a programmer too.. It can be done just by adding periority to some of scripts perior keywords(ex. single ! to be first assumed as file name and here and be applied before applying other less perior replacements).

This is not (primarily) about the syntax. The issue is that WinSCP does not support patterns in the default value, no matter what the syntax is.
https://winscp.net/tracker/743

Currently WinSCP is using an odd syntax mixing of !?&... for its custom commands.
Its not readable, and cause mistakes even for me as a programmer ..
It will be too complicated to use and for commands which contain begin and end parts for example for:



if I want to change "archive.tgz" to current selected file which is called from current syntax by ! it won't work as expected because its closing tag is same as tag for current file.

I hope at least begin and end tag characters should be at least different like <,> or [,] so when you I put a none block tag (without begin and end) like !(filename) to that container.. not mix with syntax of container pattern.