As you said :

I’d like to be able to copy 2 columns from a spreadsheet

I suppose that your selected bloc of cells ( 6 rows x 2 columns ), pasted in a new tab, within N++, is displayed, as below, where any number of the second column is simply separated, from its associated number of the first column, by a tabulation character ( \t ) !

1.25	0.25
2.5	0.5
3.25	1.25
4.5	1.5
5.25	2.25
6.5	2.75

If so, the simple regex S/R should do the job :

SEARCH (?-s)^(.+?)\t(.+)

REPLACE <controlpoint t="\1" val="\2"/> , with a space character, before the string val

OPTIONS Wrap around and Regular expression set

And you’ll get the text :

<controlpoint t="1.25" val="0.25"/>
<controlpoint t="2.5" val="0.5"/>
<controlpoint t="3.25" val="1.25"/>
<controlpoint t="4.5" val="1.5"/>
<controlpoint t="5.25" val="2.25"/>
<controlpoint t="6.5" val="2.75"/>

If you prefer separate the two values by a tabulation character, just change the Replace box, as belwo :

REPLACE <controlpoint t="\1"\tval="\2"/>

This time, you would obtain :

<controlpoint t="1.25"	val="0.25"/>
<controlpoint t="2.5"	val="0.5"/>
<controlpoint t="3.25"	val="1.25"/>
<controlpoint t="4.5"	val="1.5"/>
<controlpoint t="5.25"	val="2.25"/>
<controlpoint t="6.5"	val="2.75"/>

Best Regards,

guy038