Unable to add "follows" / "followed by" movie connections

When attempting to add missing "follows" / "followed by" movie connections between "Enola Holmes 2" and "Enola Holmes 3" in Firefox 152 running under Windows 11 25H2, the "Edit" button produces a popup dialog with the following explanatory text:

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To update connection categories such as followed by/follows, version of and alternative language version of please reach out via our contact form using the options in the drop-down.

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However, the drop-down list doesn't contain "follows", "followed by" or anything similar.