Not sure this is exactly what you want…
With Shotcut Version 18.11.18
- Detatch audio, copy audio track to a 2nd audio track. Copy then CRTL + V on A2.
- Balance filter on both audio tracks.
- Gain/Volume filter on both audio tracks. Keyframes on Gain/Volume.
With Shotcut Version 18.12.15 Beta : V18.12 BETA now available
- Now there is Keyframes on both Filters: Balance & Pan
