Dear Piya,

PT> Has anyone any insight or thought on the best translation of
PT> vitakka,sa.nkhaara,sa.n.thaana in the Vitakka,san.t.haana Sutta here?

I would interpret it here as 'santhaana' - 'appeasing'.
'sa.nkhaara' is 'a process of construing', and vitakka itself is
'vacii-sa.khaara' (a process of construing speech).

Hence 'vitakka-sa.nkhaara' is 'a process of construing thinking'.

The whole compound is then "appeasing of
thought-construing process".

PT> [My provisional translation:]
PT> If, monks, while a monk is not minding and is disregarding those thoughts,
PT> there still arises in him evil unskillful thoughts connected with desire,
PT> hate and delusion arise in him, then should turn his mind to the stilling
PT> of the thought-formation (vitakka,sa.nkhaara,santhaana) [by examining the
PT> causal sequence] of those evil unskillful thoughts. (M 1:120,18-19)

Causal sequence is examined earlier, in 'drawbacks'.

Metta, Dimitry