There are multiple ways to pass extra parameters for the softphone:

1. Pass parameters to the softphone:

Just add it to the ini file:
a) In the .ini file (brandname.ini) which can be located in the working directory (near the exe) or in the data directory  (just add your settings after the width/height parameters)
b) OR in the appfolder/softphonedef.ini file (it can be created if doesn’t exists)

Example:
[settings]
brandtext=mycoolbrand
debug=3  
(debug: 0=no,1=yes,2=extra logs and also will set the webphone loglevel to 9)
Debug 3 will also enable javascript error popups

2. Pass parameters for the softphone’s webphone engine:

\content\native\wpcfgsf.ini  (where X is the instance number, usually empty)
Pass any config for the webphone from here (this should overwrite other settings)
Ex:
autoaccept=true

3. Pass parameters from mbuild to softphone:

You can pass any parameters from mbuild in the “SOFTPHONE SETTINGS” section (it will be written to softphonedef.ini)

4. Pass parameters from mbuild to softphone’s webphone:

The old way:
Common.xxx1 = “abc”;  //string
Common.xxx2 = 7;  //int