As the title said... Sampling Editor doesnt works on Standard's Slider....
Sampling Editor is... tool/menu under the editor >>> Compose > Sample Import or accessed with ALT+Mouse Left Click in Osu!Mania
cant be quick access in Standard compose part because ALT trigger distance snap multiplier... ( can still be access through Compose > Sample Import )

BUT the problem is not that...
Even i use this method on Slider , it doesnt works, either by manual scripting and Sampler Editor...


First , about how this Sampling works... ( either by manual scripting or using this feature )
this is normal notes coding line in both standard and osu mania ( beside coordinat )

224,80,3072,1,0,0:0:0:0:

Using Sampling Editor and hitsound them, will generate this line

224,80,3072,1,0,0:0:0:100:A6S_s.wav

The last two part is Volume and Sample in used... ignoring all other 0:0: since "1,0"
which is Hitsound type ( clap, whistle , finish) : Set : and so on...




So... this is example of Slider Coding line... ( Repeating slider of 7 times, 7 times being the last or end of the slider )

144,80,2379,2,0,L|192:80,6,35,0|0|8|4|0|0|0,0:0|0:0|0:0|0:0|0:0|0:0|0:0,0:0:0:0:

(this slider has clap on 3rd , and finish on 4th )

the highlighted color , is my thought about this coding line layering and structure...



i try to read and add the 99:A6S_s.wav manually on those slider....

144,80,2379,2,0,L|192:80,6,35,0|0|8|4|0|0|0,0:0|0:0|0:0|0:0|0:0|0:0|0:0,0:0:0:99:A6S_s.wav

and yeah it doesnt works... even on any part of them...i thought it will works for each part of the slider...
thus i try to add the code between each part ( i highlighted with colour )

it doesnt works as well... my coding also has the same result when i tried with Sampling Editor ... and yes it doesnt works...
i cant find a proper line where i can add this...
this structure and layering coding line on slider seems a bit different with normal notes...



like this

224,80,3072,1,0,0:0:0:0:

i assume , they are : X,Y,offset,ComboSet,Notetype,Sound,Set,0,Custom,Volume

where
Sound: 2=Whistle, 4=Finish, 8=Clap
Set: 1=Normal, 2=Soft, 3=Drum
Custom: custom sound number

but the layering on slider is a bit different and complex... thus making the sampling method doesnt works...



In short,
Sampling doenst works on slider, any part.... , Sampling means, using a file directly hitsound to the notes ...
IGNORING timing section and it doesnt have to follow default osu custom hitsound format like Soft-hitnormal, drum-hitclap and so on...

Side note :
This works for Osu!mania perfectly...
Works for standard's single notes as well but not the slider... not at all....

Thanks for reading

144,80,2379,2,0,L|192:80,6,35,0|0|8|4|0|0|0,0:0|0:0|0:0|0:0|0:0|0:0|0:0,0:0:0:99:A6S_s.wav