If you know they are accessible from SPRO, then you can find them using the following query, which lists TCODES from SPRO customising that has been performed after installation (note the date of 2001):
SELECT distinct cobj.tcode
FROM cus_actobj cobj,
WHERE cobj.act_id = cacth.act_id
AND cacth.fdatetime > '20019999999999'
ORDER BY 1;