Window functions are powerful and very useful in Analytical data models in SAP HANA. In the past, they were generally available only in sql scripting objects like Table functions and Stored procedures but not available to use graphically in a CV.
In HANA cloud using BAS as the development tool, now it is possible to access all window functions in a graphical CV node. You can see in the screenshot below, LAG, LEAD, DENSE RANK and PERCENT RANK functions can be used directly in a CV.

Tutorial on how to do: I just created a short video on how to navigate in BAS.
https://www.youtube.com/watch?v=yIP0OrsSQFw&list=PLX8aMl9wthopz0lRBsQKdL2L2Y6-CToQ-&index=9
General help documentation for Window Functions: SAP help Documentation
Blog on evolution of HANA Tooling:
HANA Tolling
Thanks
Sreekanth