Where to place .dll files during compilation in v9.3

Due to the move to .NET 8 and the different behavior in dependency loading as such, you need to reference NuGet packages instead of single assemblies (DLLs).

Please check the documentation here (Referencing packages and files in script)  https://docs.oneidentity.com/bundle/one-identity-manager_configuration_9.3/page/sources/config/scripting/scriptreferences.htm

And you might want to check the following knowledge base article that describes how to deal with environments having no internet access. https://support.oneidentity.com/identity-manager/kb/4378808/-810086-error-compiling-script-0-0-unable-to-load-the-service-index-for-source-https-api-nuget-org-v3-index-json

HtH

but what if you've already upgraded and can't do that first compilation after the upgrade? i.e. can't use designer to edit any of the scripts?

is rollback the only option?

The compilation allows you to disable the scripts if an error occurs. You need to change the scripts after that and can re-enable them for another compilation.