More precisely it seems to be a reference to some component.
However, after searching on Google and on Matillion site, I didn't find any documentation about it. Maybe I'm bad at searching, maybe "$T" is not very SEO-friendly.
Could you send me a link to the official documentation for this functionality, please ?
As long as I have understood, this is different.: variables are written "${variable_name}" when the reference I'm looking documentation for is "$T{component_name}".