It would be very useful to have the ability to change the keybindings for inventory movement actions.

The impetus for this request: Alt+LClick is the hard-coded keybinding to invoke the action "move all of same item" which is a feature I use regularly in modpacks. With InventoryTweaks I used CTRL+Shift+LClick for this same action and I had no issues there.

Several popular Linux desktop environments have for decades used Alt as the "Mouse Modifier" key which when combined with LClick, begins a window dragging action rather than sending the click to the application. While possible to modify the Mouse Modifier key, it's a bit of a pain to do so. It's also inconvenient since it affects the behavior of the entire system just to work around a specific keybind for Minecraft.

The reason why i didnt make it configurable is because mc/forges keybind lib is fucking ass

Understandable. Even if it's not configurable at runtime via MC's hotkey system, having something like a config file that could be read once on startup would be an improvement over no configuration / changing the code and compiling it.