That would be because the values from Excel are separated by CR or LF, not by a TAB:
It is always best to develop/confirm any RegEx using Regex101.com (or similar tool)
We could write a RegEx for a specific number of Excel cells, but it might be better to write a more comprehensive macro to handle a variable number of cells, something like this:
Here is an EXAMPLE macro to give you some ideas. You will need to modify to suit you specific workflow. Please let us know if this works for you.
MACRO: Extract Excel Cells on Separate Lines [Example]
**Requires: KM 8.2.4+ macOS 10.11 (El Capitan)+**
(Macro was written & tested using KM 9.0+ on macOS 10.14.5 (Mojave))
#### DOWNLOAD Macro File:
<a class="attachment" href="/uploads/default/original/3X/4/2/4239f56d78be2e865141e12ec13806cfd8cce041.kmmacros">Extract Excel Cells on Separate Lines [Example].kmmacros</a>
**Note: This Macro was uploaded in a DISABLED state. You must enable before it can be triggered.**
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<img src="/uploads/default/original/3X/9/7/97faeb3c904aec615518062923c2489dcf312a6c.png" width="596" height="1837">