I made a report where I had performance issues with LIPS table and I found this index 'VGB' where it wasn't activated. I made the decision to activate the index and I resolved my issue. I didn't have further problems and everything is fine at least at the moment.
However, looking for a SAP Note (not related with this one) I found the '185530 - Performance: Customer developments in SD' where it indicates several strategies to make searches using certain fields in tables like LIPS and others and I realized that there was an alternative before creating this 'VGB' index.
It quotes;
...
c) Search for deliveries with sales order number (preceding document, field LIPS-VGBEL):
Incorrect: SELECT FROM lips WHERE vgbel = ...
Correct: SELECT FROM vbfa WHERE VBELV = ... and VBTYP_N = 'J' SELECT FROM lips WHERE vbeln = vbfa-vbeln
AND posnr = vbfa-posnn
...
I feel ashamed that I didn't make more research about this and I'm convinced that it would have been better to follow those instructions, however as I quoted we don't experiment issues at all and the report works fine.
My advice is always make your homework first before engaging your own solution.