I have a batch that someone marked the name of the city with the name of the publisher. Is there a way to mark all that field blank instead of each of the 300 entries separately?
Yes. To mark the fields blank, click on the first entry and use Ctrl + B to enter blank. Then click on the 6th icon from the right in the toolbar (down arrow with several black lines under it). This is the copy text from selected field into all following matching fields tool. If you do it in column entry mode, you can watch them all turn to blank.
By the same method, is it possible to change an entire column that has erroneously been marked blank instead of just being tabbed over?
@LesterChristieAnn1 . Yes (A), but (B) you don't need to correct that "error" for a non-required field.
(A) Suppose an Indexer has used Ctrl/Cmd+B on a specific field (i.e., <Blank>ed it) for every entry (a whole column if in column mode). You can (1) use the backspace or delete key to remove that <Blank> indicator from the first entry. You can then (2) use that "copy to all following matching fields" tool on the now "empty" first entry to render the whole column (i.e., that field in every entry) empty.
However, a required field (indicated by a * to the right of the Field Name) must have something (at least <Blank>) indexed in it and must not be left empty; and I thought that all fields were required these days. But I haven't examined every project.
(B) Also, it is OK to blank (Ctrl/Cmd+B = <Blank>) a non-required field instead of tabbing over it (i.e., leaving it empty) - no need to "correct" that situation. It's just extra work to do a Ctrl/Cmd+B rather than to tab over it; that's why they suggest tabbing over it. But, the system treats a non-required field the same whether it is empty or has the <Blank> indicator in it - ignores it.