Set Main Line = True already set on your Saved Search Criteria because Only searches filtered to the main line support editing.
If this doesn’t work , see below
If we have marked the Use Expressions checkbox.
According to Field Help, if this option is enabled for a search, inline editing is disabled in list, dashboard, and sublist views based on that search. If you want inline editing to be available for a view, ensure that the Use Expressions box is not checked for the search that filters view results.
Also, this standard behavior is logged as Enhancement 144046 Search > Inline Editing / Direct List Editing > Use Expressions = T in some searches (ex. Transaction, Item) will disable DLE.