I can see TIgnoredErrors in the API documentation, but I cannot find any public API on TExcelFile/TXlsFile to assign ignored errors to a cell range. Is this feature supported in the VCL edition, or is TIgnoredErrors only an internal type used when reading/writing existing files?
TIgnoredErrors is actually part of a work in progress. We are working in adding this functionality to FlexCel, but it still isn't finished, and sadly today you can't do that programatically. It should be coming in a new release, I am not sure if the next or later, but we are working on it. I'll try to up its priority so it can be in the next release.