Support for advanced regex in File Mask

Hi,
I have been using File Mask to conditionally copy files.
However if I use advanced regex in file masks, it doesn't seem to be working.
For example, file mask for including *.txt works fine but .*([.]txt[_]\d{14}) doesn't seem to be working even though my target filename matches with the mentioned regex.

For now, as a work around I used *.txt_[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9] where selecting each digit individually 14 times in my case.

Want to know if only the basic file_masks mentioned at https://winscp.net/eng/docs/file_mask#basic are supported or more.

Thanks

What is documented is supported only :)
For regex support, see:
Issue 1617 – Regular expression support when finding files