I hope it's OK to post this here. After noticing the script from VajskiDs here: https://github.com/L10N37/Batch-Convert-multi-BIN-to-single-BIN I managed to optimize it a bit to make it portable, basically no need to edit any paths anymore.

The Convert_MultiBIN2Single.bat (The code may look different here, as it should be in NP++ as an example.)

@REM Portable Multi-BIN to Single-BIN Batch Script v2.0 by m3Zz
@ECHO off
CLS
SET chdmanpath="%~dp0chdman.exe"
SET sourcepath="%~dp0\MultiBIN"
SET workpath="%~dp0\_TEMP"
SET destpath="%~dp0\SingleBIN"
FOR /R "%sourcepath%" %%R IN (*.cue) DO ( 
%chdmanpath% createcd -i "%%R" -o "%workpath%\%%~nR.chd" -f 
%chdmanpath% extractcd -i "%workpath%\%%~nR.chd" -o "%destpath%\%%~nR.cue" -ob "%destpath%\%%~nR.bin" -f
DEL "%workpath%\%%~nR.chd"
)
EXIT

You still need the "chdman.exe" (I used the latest v0.239) at the same place as the *.bat. It can be extracted with 7-Zip from the downloaded "mame0239b_64bit.exe" here: https://www.mamedev.org/release.php

So, create the *.bat anywhere you like with the code above, place the chdman.exe next to it and also create the folders "MultiBIN", "_TEMP" and "SingleBIN" at the same place. All in one folder. Now simply place all your multiple BIN games (PSX/PS1 incl. tracks) you want to convert into the "MultiBIN" folder and run the script. It will convert them first to CHD and single BINs with CUE.

This "%~dp0" defines the path from where the *.bat was started, which makes the whole thing portable. I also added a "chdmanpath", to get an useable value for that if needed. All those can be changed to your liking, but right now there's no need for a full path to anything. Between the brackets is the loop.

All unnecessary lines are removed (REM, etc.) from the original script. For me, there is no need for any further description, the script now works out of the box and basically explains itself. No need for multiple chdman.exe's any more (before it needed to be in the temp and sourcepath). I packed myself a Zip with the "Convert_MultiBIN2Single.bat" + chdman.exe + the empty folders and can extract the anywhere for instant use.

So, I hope it helps , because it took some time to change it. Important seems to be, that the folder structure, equal if you use a portable path or full path, has no spaces. My 1st problem was a single space in one folder name, like this "G:\E_STUFF\EMU_TOOLS\02 ISO-Image\MultiBIN2Single". After changing it to "..\02_ISO-Image.." it worked like a charm.

If needed, I uploaded the package (bat + exe + empty folder) to Zippy and Uptobox, and also some mirrors:

https://www54.zippyshare.com/v/XK9l6qkN/file.html
https://uptobox.com/69lt2m57oboy
https://mirrorace.org/m/3Mr7u
https://multiup.org/download/6a909d543fbe8a69b5f8487d67641003/MultiBIN2Single%20v2.0%20by%20m3Zz%20%28for%20PSX%20BINs%29.7z
https://www.mirrored.to/files/1DK1MTHV/MultiBIN2Single_v2.0_by_m3Zz_(for_PSX_BINs)_0.7z_links

Greetings!