gd-5.txt
Wddss-5.txt
Hf-66sa-7.txt
...
for /f "tokens=* delims= " %%i in ('dir /b "*.txt"') do Set LIST=%%i& set LIST | ren "%%~fi" "%LIST:-=%"
SetLocal EnableDelayedExpansion
for /f "tokens=* delims= " %%i in ('dir /b "*.txt"') do (Set LIST=%%i & ren "%%~fi" "!LIST:-=!")