Environment variables in FirefoxPortable.ini

Hello,
I wonder if it is possible to use environment variables in path name in the FirefoxPortable.ini file, for instance %username%, %appdata%.
There are several profiles on the family PC and I would like to save each profile datas in the specific %appdata% directory.

I tried to set the "ProfileDirectory=" in the FirefoxPortable.ini file that way :
ProfileDirectory=..\..\..\Users\%USERNAME%\AppData\Roaming\FFdirectoryName\Data\profile
... but it didn't work.

I tried the following and it works :
ProfileDirectory=..\..\..\Users\ProfileName1\AppData\Roaming\FFdirectoryName\Data\profile
And so for the settings and plugins directories.

I know FirefoxPortable2ndProfile and use it already, but I can't with it save the different profile datas in each %appdata% directory.

I can write a batch to launch FirefoxPortable aiming at the right %appdata% by changing each time the FirefoxPortable.ini file, but it would be simplier to use the environment variables in it.

Is it possible ?

Regards.