You would define and then use attribute-sets, you can use them anywhere.
You use something like this:
<xsl:attribute-set name="row-style">
<xsl:attribute name="padding-top">0pt</xsl:attribute>
<xsl:attribute name="padding-left">3.5pt</xsl:attribute>
<!-- rest of your attributes you wish here -->
</xsl:attribute-set>
and then on the actual object:
<fo:table-row xsl:use-attribute-sets="row-style">
Also note that if you have repeatable chunks you wish to reuse, one definition of an attribute-set can use another in the same way, like:
<xsl:attribute-set name="row-style" xsl:use-attribute-sets="inherit-me">