Custom Workflow Activity/Plugin that edits a different entity than the one that activates it

Hello,

I am trying to use a custom C# CodeActivity to update a different entity than which entity triggers it. I have been trying to use Microsoft.Xrm.Tooling.Connector CrmServiceClient to achieve this, although I am getting the error message "Could not load file or assembly 'Microsoft.Xrm.Tooling.Connector, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified." Any suggestions?

.NET Framework 4.6.2

All NuGet packages are on current stable versions and all appear to be compatible (Microsoft.CrmSdk.XrmTooling.CoreAssembly version 9.1.0.108)

Thank you!