manigteáw-ness
This might be just a supplemental entry adding to an entry in the Main Volume.
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
manigteáw-ness
AddÐæt sunnan gér byð gesett on þrím hund dagum and fíf and syxtigum dagum and syx tídum þæs þe ásmeáde séo msenigtýwnes geþungenra wera, Angl. viii. 298, 5.
This is a supplementary entry with editorial changes to an entry in the main volume of the dictionary. Look under the 'Possibly connected entries' below, or for the same headword in the list to the left.

A Combined List of Abbreviations.

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A Combined List of Abbreviations.