It is important to remember that it is not possible to extract texts longer than 60 characters as the key into an infoobject in BW 7.3. SAP documentation states that longer character strings are possible in BW 7.4, but I have never worked with it. There are methods using multiple text attributes and concatenation to present longer texts, but again, there are practical limits to this method.
Here is the method I have used with some success for long texts in BW 3.x and then migrated to BW 7.31. We are also looking at CRM notes, and we will need to use this method. Unfortunately CRM notes can have lengths that produce multiple pages of results, and using the BW method documented below would result in a foolish approach.
Long texts in SAP BW: Modeling
Ultimately BW is really not appropriate for this sort of reporting. It would be better to design a custom report with notes in CRM Directly.