I feel like the editor should have a seperate tab specifically for hitsounds, it has a tab for timing, storyboard, compose, etcetera. Why not make the hitsounding processs easier by having it in its own tab.
Here is a super simple draft of what i imagine somthing like this might look like that i made in ms paint.

https://ibb.co/6cCmQQGg
The idea is that instead of choosing a sound for each hit circle, you choose a sound for each lane and then drag the hit circles from the unused lane into whatever lane you want. This (in my opinion) makes it a lot easier to add hitsounds because of their non-unique nature, and makes hitsounding a drum loop for example much easier. I also think it helps greatly in visualising where hitsounds are playing in the beatmap.
Just some notes about the draft:
1. The numbers on the hitcircles correspond to thier volume, not combo. And i think it would be intuitive to use the scroll wheel while hovering over them to change their volume.
2. The "+" is intended to open a menu where you can choose a sound for that lane, upon choosing the sound, the "+" would move to the next lane on the right.
3. Once enough lanes have been added that there is no longer space to the right to add more lanes, a horizontal scroll bar should appear that lets you scroll to reach further lanes. A hot key like Shift+Scroll would also be useful here as to not rely on the bar.
Here is a super simple draft of what i imagine somthing like this might look like that i made in ms paint.
https://ibb.co/6cCmQQGg
The idea is that instead of choosing a sound for each hit circle, you choose a sound for each lane and then drag the hit circles from the unused lane into whatever lane you want. This (in my opinion) makes it a lot easier to add hitsounds because of their non-unique nature, and makes hitsounding a drum loop for example much easier. I also think it helps greatly in visualising where hitsounds are playing in the beatmap.
Just some notes about the draft:
1. The numbers on the hitcircles correspond to thier volume, not combo. And i think it would be intuitive to use the scroll wheel while hovering over them to change their volume.
2. The "+" is intended to open a menu where you can choose a sound for that lane, upon choosing the sound, the "+" would move to the next lane on the right.
3. Once enough lanes have been added that there is no longer space to the right to add more lanes, a horizontal scroll bar should appear that lets you scroll to reach further lanes. A hot key like Shift+Scroll would also be useful here as to not rely on the bar.