I have IBM Streams 4.3 and wish to update a toolkit not available on public GitHub. Is that possible?
Yes, it is possible. By using your IBM Streams license and your account to IBM Fix Central server, you can download the complete set of the specialized product toolkits.
This is the direct link to the Fix Central server: https://www-945.ibm.com/support/fixcentral/swg/selectFixes?parent=ibm%7EInformation%20Management&product=ibm/Information+Management/IBM+Streams+Toolkits&release=4.3.0.0&platform=All&function=all
The release (4.3.0.0-i20181113) includes 2 new toolkits: