The custom part is there to allow you to add any "special" parameter you want... So you can add ine custom parameter in the fixture builder and then named it "macro" (but with 4 letters to allow you to read it easily at the bottom of the fader), and after this you will have a macro fader in the custom part... now if you really want to use fader you shown in the the misc part, just add a prism parameter, and in the edit window add a rotation fonction and set it to the macro chanel of your bar....
but now the simplest solution is to use the macro parameter, for each intern programm you set a slot , and then in cuelux when you will click on the macro number 1 iit will start the first program, and same for any other macro...
Nowa bout LSB , you now dmx is coded on 8 bits so you can only get 255 different states, if you want to get more different states you can code on 16 bit but this way you have to use 2 chanels, so one chanel will be the first 8 bits and the second one will be the last 8 bits ( this way you have your 16 bits) so to know wich chanel is the first bites and wich one is the last bits, you use LSB and MSB (low significant bit and Most significant bit), so in the builder control is the bits from 8 to 16 and control LSB is the bits from 0 to 7...