Why? Unraid is Based on Slackware and Slackware is well documented.
I cross compile most everything on or better speaking in a Debian Bullseye Docker container (customized to my needs) because I'm most familiar with Debian and Docker because I don't have to .
What do you need exactly? If you want to install packages that are not shipped via nerd tools then compile it somewhere on Linux and create a package or copy it over to Unraid.
If you want to set up your own dev environment directly on Unraid, which I don't recommend because you have to install the packages on every reboot and so on, you can also pull packages from the official repository for Slackware 15 here (since Unraid 6.10 is based on Slackware 15) or for packages you don't find you can try to find it from pkgs.org
BTW Sorry for the late answer but I'm not subscribed to every thread where I posted...