.NET Assemblies tab for .NET/.NET Core processes was added to Process Explorer v17.09 - https://techcommunity.microsoft.com/blog/sysinternals-blog/coreinfo-v4-0-notmyfault-v4-30-and-process-explorer-v17-09/4478567
Please note that this works for non self-contained .NET apps (this will be added in future versions).