Maybe I did not understand your question.
The Ctrl + U volume control or speaker button is the output volume for speakers, there is no issue with editing.
To change the volume of a clip as a whole, in the timeline, drag the sound line up or down.
If you want to adjust the volume on specific parts of a clip, hold the Ctrl key while clicking the sound line, a white ball appears, drag to adjust to that position.
Another way to adjust, select the audio in the timeline, click the Keyframe button, in Volume you can make fine adjustments.
XEON-E5-2680 v4 / Mem. 16GB DDR4
M.2 NVME 512Gb / 2-SSD Sata3 1TB
AMD RX570 / Display Philips 272V8
Windows 11_64Pro / PD22/365