[chaley]

It works for me, at least as far as I can test it not having a Palm TX.

My experiment:

1. Create a text file containing one word, "Foobar"
2. Import that text file into calibre
3. Using edit metadata, set the author to "An empty book to delete later"
4. Set the series to "Some Series"
5. Set the series index to 42
6. Convert the book to epub
7. Set the template of a composite column to "{title} - {series}[{series_index}]"
8. Set the save template for save to disk to "{#composite}"
9. Add a metadata plugboard "any format:save_to_disk = ([{#composite}] -> title)"
10. Save the newly-added and -converted book to disk

Results:
Calibre debug log showing that the plugboard was used during save-to-disk:

Job: 4 Save books (0 of 1) finished
Save books (0 of 1)
        Save-to-disk using plugboard: txt [(u'{#composite}', 'title')]
        Save-to-disk using plugboard: epub [(u'{#composite}', 'title')]

File name in the saved-to folder showing that the save template was used:

empty book to delete later, An - Some Series[42].epub

Content of opf file inside the saved book showing that the metadata plugboard was used and the title is set as expected:

<?xml version="1.0"  encoding="UTF-8"?>
<package xmlns="http://www.idpf.org/2007/opf" version="2.0" unique-identifier="uuid_id">
    <dc:creator opf:role="aut" opf:file-as="Author, None">Author, None</dc:creator>
    <meta name="calibre:series_index" content="42.0"/>
    <meta name="calibre:title_sort" content="empty book to delete later, An"/>
    <dc:title>An empty book to delete later - Some Series[42]</dc:title>

I did the same thing with the folder device: set up the plugboard, connect to folder, send book to device. The debug log shows that the plugboard was used, and the title attribute in the epub's metadata is the same as above.