Shifting text markup and reharsal marks

[Antonio PALAMA']

I understand that the official method to shift a text markup vertical is

\property Voice.TextScript \override #'padding = #N

I also seem to understand that the units used are the separation of 
staff lines
and that the instruction increases the minimum distance of the text to other
objects.

My question is:

Is there a method to specify an absolute vertical shift of the text in 
metric units e.g. \mm or \cm?
I there a method to specify horizontal shifts?

Thanks for your help,

Antonio Palama'