Thank you, RSF, putting css paths to variables works!
However, it appears that the path (everything inside the square brackets) must be inside one variable, you cannot split it into: %html[%table-row-path>%table-td-path]
Instead you first need to combine those two paths into one var:
%whole-path = %table-row-path>%table-td-path
and then simply do %html[%whole-path].
Or you may write the whole path variable in one go:
%whole-path = tr:nth-child«%tr-num»>td:nth-child«%td-num».
spo