Diag4Bike is a "programmer" for the bike, it aint cheap (like $1200), and you have to have a windows base computer to hook it up to and install the software on (a laptop cause you're gonna want to take it out into the garage).
In the US you can find a dealer in your area for Hard Drive V Twin products at their site https://hdtwin.com/dealer-locator

Here's Diag4Bike in their catalog, page 478-479,
http://catalogs.wps-inc.com/2022/vtwin/478/

I got the #867-02005, and my dealer gave me 15% off. One of the HD dealers near me was my "local dealer" for HD Twin products...
Here's the "manual", so to speak for it, most everything for programming is under "Toolbox"... https://doc4bike.actia.cz/en/diagnostics/

It doesn't marry to a bike for the diagnostic stuff, and you can use it on as many as you want with what comes with it. If you want to do tuning stuff then you pay for a tuning license for each bike you want to tune, at like $70 each (I think)... I don't tune...