"Open in Solid Edge" is not available in the content view for Solid Edge assemblies. It is available for other file types, and for assemblies in other views.
The Teamcenter preference "AWC_AlternateSelectionCommandsList" needs to have the value "Awp0OpenInSEEC". Add that value to the preference and close and reopen Active Workspace on the clients to resolve the issue. This should work for standalone Active Workspace and hosted Active Workspace.
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