How to rename only sub-folders without changing parent folder names - windows

Question

I have a folder containing several hundred sub-folders in the format Name, ID. Each of these folders contain several sub folders, some of which contain spaces in their names. I would like to rename only the sub folders and not the parent folders by replacing the spaces with underscores, e.g. C:\Location\John, 1234\My Documents to C:\Location\John, 1234\My_Documents.
I have tried modifying a piece of script I have found on here but it changes the parent folder as well
Here is the unedited code:
#echo off
setlocal EnableExtensions DisableDelayedExpansion
set "StartFolder=C:\Tydelik"
cd /D %SystemRoot%
set "RenameError="
rem Rename all folders containing at least one space character in folder name.
for /F "delims=" %%I in ('dir "%StartFolder%\* *" /AD /B /S 2^>nul') do call :RenameFolder "%%I"
if defined RenameError echo/& pause
rem Restore initial environment and exit this batch file.
endlocal
goto :EOF
:RenameFolder
set "NewFolderName=%~nx1"
set "NewFolderName=%NewFolderName: =_%"
set "FolderPath=%~dp1"
if not exist "%FolderPath%" set "FolderPath=%FolderPath: =_%"
set "FullFolderName=%FolderPath%%~nx1"
if not exist "%FullFolderName%\" set "RenameError=1" & goto :EOF
for %%J in ("%FullFolderName%") do set "FolderAttributes=%%~aJ"
if "%FolderAttributes:~3,1%" == "h" %SystemRoot%\System32\attrib.exe -h "%FullFolderName%"
ren "%FullFolderName%" "%NewFolderName%" 2>nul
if errorlevel 1 goto ErrorFolderRename
if "%FolderAttributes:~3,1%" == "h" %SystemRoot%\System32\attrib.exe +h "%FolderPath%%NewFolderName%"
goto :EOF
:ErrorFolderRename
echo Error renaming folder "%FullFolderName%"
set "RenameError=1"
if "%FolderAttributes:~3,1%" == "h" %SystemRoot%\System32\attrib.exe +h "%FullFolderName%"
goto :EOF
As I said the expected output for each sub folder should be C:\Location\John, 1234\My_Documents instead of C:\Location\John, 1234\My Documents. Currently with the code I have, I get C:\Tydelik\John,_1234\My_Documents.

Answer 1

While Compo's solution renames folders "depth=2", this renames just the "leafes" (very last folders of a tree, "depth=last"). I kept your call approach to avoid delayed expansion and resulting possible problems (folder names with ! - unlikely in your situation, but one never knows...)
#echo off
setlocal
set "sourcedir=..\..\"
for /f "delims=" %%I in ('dir "%sourcedir%" /ad /b /s 2^>nul') do call :RenameFolder "%%I"
goto :eof
:RenameFolder
dir /ad /b /s "%~1" 2>nul | find /v "" >nul && goto :eof ::skip renaming, if a subfolder exists
set "leaf=%~nx1"
ECHO ren "%~1" "%leaf: =_%"
goto :eof
Note: for security reasons I disabled the ren command by just echoing it. If it works as intended, remove the ECHO.

Answer 2

Here's an example of what I think you're looking for, based upon the fact that you're interested only in renaming subdirectories of "C:\Tydelik\Name, ID", not any contained within those subdirectories:
#Echo Off
SetLocal DisableDelayedExpansion
Set "SourceDir=C:\Tydelik"
For /F "EOL=?Delims=" %%A In ('Dir /B/AD "%SourceDir%" 2^>NUL'
)Do Set "TargetDir="&For /F "EOL=?Delims=" %%B In (
'Dir /B/AD "%SourceDir%\%%A" 2^>NUL') Do (Set "TargetDir=%%B"
SetLocal EnableDelayedExpansion
If Not "!TargetDir: =!"=="!TargetDir!" (
Ren "%SourceDir%\%%A\%%B" "!TargetDir: =_!")
EndLocal)