It is currently impossible to create deep links to objects in 3rd party community widgets that open Connections, the widget and the desired object within the widget.
The reason is that the community widget can not „see“ any additional url parameters attached to the standard connections url.
Inside of the IFrame custom app, there is a mechanism where the app sends a message „appready“ and gets a response from connections with some environment details like widgetID, CommunityID, User etc.
For allowing to create a deep link which opens a specific object inside of the custom app inside of the IFrame widget, we would need a way to transport the object ID or search term from the link into the 3rd party app.
If the response message from connection to the appready message would contain the complete current URL, we could use this in a new way:
1. the user receives a deep Link like <Standard Link to Community widget>?newURLParameter=12345
2. the Link leads to logging into connections, loads the Community and jumps into the 3rd party widget
3. App sends appready, Connections answered with the message, containing the complete URL
4. App recognizes the custom URL parameter and highlights object number 12345
That way, a deep link could work with very little modification of the solution.
And Microsoft was faster than us again: