How do I convert a "______" to "NULL" in a string column?

I’ve tried the String Manipulator, but it seems to have issues with the “______”. I am new the KNIME, but what have I missed here please? The space is 6 underscores - is that significant?
TIA

@Tropicpalm welcome to the KNIME forum.

One option ist the String Manipulation:

regexReplace($column1$, "^ {6}$" ,toNull(""))

Or you can use the Column Expression:

if ( equals(column("column1"), "      "))
{toNull("")}
else {column("column1")}

String insert NULL - KNIME Forum (76691).knwf (77.2 KB)

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