Open your startbutton.xml file with notepad.exe

Use Ctrl + F to open the find dialog box and type in part of the code to skip down to where you need to be. Each slider is named appropriately so searching for MasterSlider in the search box should bring you down to the area you want to edit (beginning of the sliders coding) and then just look thru and change each slider to match what values you want.
 
For sound sliders...

UpperLimit="20" Value="number here will vary"

change the value="put in your number here from 0 to 20" to a higher number to increase volume or a lower number to decrease (dont change the upperlimit just referencing that for where to look for the value number to change), whatever the number you put in divide it by 20 and that will give you the number it will show on slider in game, like if you want sound at max 1.000 change it to value="20" or if you want something in between can just throw in whatever number your looking for, like if you want 0.250 as the number on the slider shown in the mod, it would be value="5"

next change this part (it will vary to match slider name):

Combat_music_Volume="0.050"

like in the above example if you set value to 5, using the math 5/20 would equal 0.250 as I noted above, you would change the "0.050" to "0.250" to match

For shader slider...

the settings for the shader works slightly different...

instead of the value="x" being divided by 20 as in the sound files it is instead multiplied by 15

so if you want to set the shader to say 150 instead of 300, you would lower the value (instead of increasing) to value="10"

again make sure not to mess with the upperlimit number or any of the equation numbers

then goto the r_fast_layer_min_distance="300.000" line and change "300.000" to "150.000" to match the new change

hope that helps for setting up your slider values to more preferrable ones for your needs