Introduction
When one searches for special things from the ABAP Netweaver Stack like RZ11 parameters and types eg "max_amc_receiver_entries" into the search box on help.sap.com you get only results from 2017. But this parameter was available before 2017 and is still available in current versions!
Temporary Solution
When you are specifically looking for search hits in a concrete ABAP/NetWeaver version, use the following version specific landing pages
https://help.sap.com/nw74
https://help.sap.com/nw75 or
https://help.sap.com/viewer/product/SAP_NETWEAVER_750
https://help.sap.com/nw751abap
https://help.sap.com/viewer/product/ABAP_PLATFORM_1809
https://help.sap.com/viewer/product/SAP_S4HANA_ON-PREMISE/1909
https://help.sap.com/viewer/product/SAP_S4HANA_ON-PREMISE/2020
and type in your search term on those pages, then you will get results!
But there are still some inconsistencies:
Final Solution
SAP should make sure the search on help.sap.com works and gives the expected hits, that the link provided in the search results works, that the product restriction for search results works and that pages have titles.
Updates
27.09.2021: Added some more version links