I cannot seem to find a manual with instructions on how to program ADKS and AKYD for a DT750 and an 8 button Desiless IP set on a SV8500.
Can anybody point me to the right documentation?

Try the command manual under AKYD. Also the peripherals manual, book 3.

Here you will get the user manual of SV855 https://www.necall.com.au/products/telephone-systems/nec-sv8500/

In this page in footer you will get brochure and system specification of SV8500

Thanks to everyone that replied....I have no idea how I missed this, but the answer I was looking for is spelled out in the ADKS command in the command manual...cartoons and everything.

Sir , you need to program the KEY on the DT750 the FKY=165 SPD name display and all other keys as SPD keys FKY =59 then go to phones and program the one touch key with name

1- press the SPD name display
2- press the SPD key
3- fill the name
4- select feature key + the SPD key with name + ext number or out number + feature a gain now you will have SPD key with name once press it the call will be start