Our code signing keypair is going to be stored in Azure Key Vault. Will we be able to use install4j from EJ Technologies to do application code signing with the key stored in Azure Key Vault?
There is no integration with Azure Key Vault mentioned here.
As of install4j 10.x, there is no direct support for Azure Key Vault. However, you can use
https://github.com/vcsjones/AzureSignTool
and the "Executable processing" step in the Windows media wizard to sign with Azure Key Vault.