I'd like to be able to delete all rows in a Google Spreadsheets where a given text string exists anywhere in the row. The text being searched for could be in any cell in the row, and also could be part of a longer string within the row cell e.g. "xxxx [text being searched for] yyy".
I think I understand your question. Have you tried using the search and replace feature? I believe there's an add on for that if sheets doesn't have it by default.
You have not tagged this google-apps-script but with a script is the only way to delete rows 'automatically'. However 'manually' is not tedious. Assumimg your range of interest is confined to ColumnsA:Z, in say AA1 please try:
and copy it down to suit, where
text above represents whatever the offending string is.
This is case insensitive.
Then filter ColumnA:A to select rows that have a numeric value (not
0) and delete these.