Using the 'Create related idea' option within a feature creates an idea that is promoted to that feature, and shows it in the Research tab of the feature. But if the idea is then promoted to a different feature afterwards, there will be no visible relationship left between the records meaning that some history is lost.
Below is a step-by-step overview of the process we followed:
A related idea (I1) is created in the Workspace W1 from Feature A in Workspace Name: W2.
The research tab highlights the link between the idea and feature. This link was previously established through the related tab before the release of the research tab.
Once the idea (I1) in W1 is promoted to a feature within the same workspace, the link under the research tab for Feature A in workspace W2 is removed.
Please find attached a screen recording of the test performed on our sandbox workspaces.