I want to update a dataset programatically outside of WealthLab.

I created a new XML file, preserving the xml syntax but replacing with new values. The Data Manager
didn't see the new file. I closed and opened the Data Manager panel, it still didn't see it. However,
when I restarted the program it saw the new file.

I tried the same thing with an existing xml file. I removed the symbols and replaced with new ones.
However Data Manager still saw the existing symbols not the new ones.

Is there a way to force data manager to re-read the files, without restarting the program. ?

QUOTE:
Is there a way to force data manager to re-read the files, without restarting the program. ?

No and you can find it mentioned on the forum elsewhere - for instance, here's what comes up if I search for "programmatically":

Creating a DataSet programmatically
How to create Dataset dynamically?

Thanks Eugene. My question was not how to create it programatically, but rather how to get it loaded after modification without restarting WL.

A feature request: add a "Rescan" button in the data Manager panel to rescan and reload the xml files.

You're welcome.

QUOTE:
A feature request: add a "Rescan" button in the data Manager panel to rescan and reload the xml files.

If you give your request an extra thought, you'll quickly arrive at how obscure and unnecessary it would be in the normal modus operandi. The DM interface is streamlined and elegant, and out of the blue here comes a button whose purpose cannot be explained to 99.5% users of WL. So, the solution is to simply restart WL.