Hi,
I understand you would like to set up TREX search in notes of IR documents.
Notes search is nothing hard for TREX - please check in tcode ESH_MODEL for template CRM_BUS2000126. and in it for text subcomponents - like BTTEXTH.
this is responsible for indexing notes.
in ESH_COCKPIT you can schedule indexing of this template.
BR
Radek