I'm not sure if there is an option hidden somewhere - possibly, and I'm sure if
there is someone will find it!

I'd do it like this:

* Column select all of file 2 and copy
* Position cursor at the first line of file 1, at the end and add enough spaces
to be after the longest line, plus 4 or more spaces [see below]
* Paste
* Ctrl+End, RegExp S/R:
  Search: ^(.+\S)\s\s\s\s+(\S.*)$
  Replace: $1$2

The regexp reads: From the start, grab anything that doesn't end in a space and
save in $1, skip at least 4 spaces, then grab anything not beginning in a space
up to the end and save in $2.

If any lines contain a lot of spaces it might get a bit confuses, but it will
work fine in 99% of cases.

Example position (the vertical bar "|" is the cursor pos, red dots are added
instead of spaces because they're collapsed in HTML)


I[color=red].......................[/color]_|_
do
not
know
where
family
doctors
acquired
illegibly
perplexing
handwriting;
nevertheless,
extraordinary
pharmaceutical
intellectuality,
counterbalancing
indecipherability,
transcendentalizes
intercommunications'
incomprehensibleness.


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