1. Import task has these two qualifiers:

displayerror
displaylog

They do not affect import.

2. No. If you check exported xml, you can see that exported tasks do not contain IDs, so, on import they could not overwrite existing tasks. Not sure about how correlate/next work on ID fields btw.

Exporting and importing what is currently present is the best way. 

It's the easiest way. The best way would be to write and document  a script (ObjectScript code) that transforms base instance into what they need. This way changes are documented and adding another server is easy.

1. Execute this to get a list of available flags and qualifiers:

Do $System.OBJ.ShowQualifiers()
Do $System.OBJ.ShowFlags()

Qualifiers are preferable to use.

2. I'd rather go with programmatic access. Write code that's:

• Opens system task object
• Modifies and saves it

What system task did you modify?

Please post the code you use to generate xml.

Do you want to pull all the rows each time?

If so,  just clear “key Field Name”  setting and BS would process all rows every time it's run.

Compilation is usually multi-process, I'd try single-process compilation and see how it works:

$SYSTEM.OBJ.Compile(.classes, "/multicompile=0")

Multicompile qualifier:

           Name: /multicompile
    Description: Enable use of work queue manager (optionally specify the number of workers if value >1)
           Type: string

UPD. Who throws a RESJOB? Do you want to kill compile process from external process (that was my idea)? Or do you want to terminate abnormally?  If it's the second you need to check errolog from Compile method and terminate the process explicitly:

do $system.Process.Terminate(, 1)

Also I wrote a series of articles on managing Continuous Delivery process. Check it out.

If Is it only Cache SQL, where did you learn about it?

From documentation. Here's a link to SQL reference.

About XLSX files, they are not one XML but a ZIP archive with arbitrary large number of xml files referencing each other.

For example there is a separate XML file for cells' text values.

It's possible to extract information from it but it seems a rather daunting task.

Here's a example of a direct manipulation of a Docx file.

There are several approaches available:

1. Automatic conversion of XSL(X) to CSV is possible using LibreOffice. Here's an article on how to do that.

2. Use Java library, such as Apache POI to traverse the cells and send results back. To send results back quickly and efficiently you can use String[] type and fill it with $lb built on Java side. String[] would become %ListOfDataTypes in Cache and $lb would remain $lb.

I've done some preliminary work but didn't get around to finishing or publishing it so here's a sample code that outputs list to console:

package isc.poi;

import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.usermodel.Row;

import java.util.ArrayList;
import java.util.Iterator;
import java.io.File;

import static org.apache.poi.ss.usermodel.CellType.*;

public class Main {

    public static String ROWSEPARATOR = "\t\t\t";

    public static void main(String[] args) {
        try {
            Test1();
        } catch (Exception ex) {
        }
    }

    public static String[] Test1 () throws Exception{
        ArrayList<String> list = new ArrayList<String>();

        File file = GetFile();
        Workbook workbook = WorkbookFactory.create(file);
        Iterator<Sheet> sheetIterator = workbook.sheetIterator();
        while(sheetIterator.hasNext()){
            Sheet sheet = sheetIterator.next();
            String name  = sheet.getSheetName();
            String value = null;

            Iterator rows = sheet.rowIterator();
            while (rows.hasNext()) {
                Row row = (Row) rows.next();

                for(int i=0; i<row.getLastCellNum(); i++) {
                    Cell cell = row.getCell(i, Row.MissingCellPolicy.CREATE_NULL_AS_BLANK);
                    if (cell.getCellTypeEnum() == FORMULA) {
                        switch(cell.getCachedFormulaResultTypeEnum()) {
                            case NUMERIC:
                                value = String.valueOf(cell.getNumericCellValue());
                                break;
                            case STRING:
                                value = cell.getRichStringCellValue().getString();
                                break;
                        }
                    } else {
                        value = cell.toString();
                    }
                    list.add(value);
                    ///System.out.print("'" + cell.toString() + "'"+" ");
                }
                list.add(ROWSEPARATOR);
                System.out.println();
            }


            /*for (Row row : sheet) {
                for (Cell cell : row) {
                    System.out.print(cell.toString()+" ");
                    //int i=1;
                }
                System.out.println();
            }*/
        }
        String[] result = list.toArray(new String[list.size()]);
        return result;
    }

    public static File GetFile () {
        File file = new File("D:\\Cache\\POI\\Book1.xlsx");

        return file;
    }

    public static Object Test(Object in)
    {
        String[] ret = new String[1];
        ret[0] = "144";
        return ret;
    }
}

Try to check who calls GetBatchHeader and what it returns.

At a glance, I think it's called from GetBatchObject method of EnsLib.RecordMap.Service.BatchStandard class:

Set tStatus = $classmethod(..BatchClass, "GetBatchHeader", pIOStream, pTimeout, .pBatch, .pLookAhead)
If $$$ISERR(tStatus) Quit

Check that tStatus is not an error, fix GetBatchHeader it if it's an error.

As I originally said

Note that changing value back would still mark property as modified.

Any change (except immediate same value) would set m%PropName to 1.

I think that checking m%PropName and only if it equals one additionally checking GetStored would work faster.

m%PropName returns 1 if the property value was modified, 0 if not.