Prepending timestamp before wildcard with GET will overtype original filename

Hello, I'm using a simple get script to grab files, and I'd like to put the timestamp at the beginning of every downloaded filename.

ie:

if the file it grabbed was named thisisafilename.txt, the downloaded file will be named 20190121-lename.txt as if it is in overtype mode. Is there a way to use insert mode with renaming instead?

No it's not possible.

You can use WinSCP .NET assembly from a PowerShell script instead:
See https://winscp.net/eng/docs/script_download_timestamped_filename#library

Or you can rename the downloaded file after the transfer using Windows [batch file] commands.