I don't think that's the purpose of this mod homie. Cant select multiple items at once because you're supposed to use the inventory system like games like DayZ and Tarkov. Gotta move them one at a time or use the shortcuts to move in a single click.

Interesting, a lot of other mods contain a variety of customizable settings so the player can choose their optimal playstyle. I like the visual design of the mod and accessibility of having multiple bags open at once, but the tedium of sorting would be nice to be adjustable.

Is there a way to swap the position of 2 items? Like if I drag Item A over Item B, I want them to switch positions on the grid, but not finding it possible unless I'm missing a hotkey.

At the moment item swapping is not supported.
In the future I have additional control options planned for Beta 7, but for now the focus is on Beta 6, which is to add controller support and clothing pockets, as well as rebalance the mod now that I've had time to properly playtest it.

There is no way to multi-select, your best option to to ctrl-click each item to rapidly transfer.
The selected inventory on the player character is prioritized to receive items when using ctrl-click.
(controls are rebindable via mod options)

Item swapping I might get into the next update, we'll see. Shouldn't be too hard to add and is definitely a QoL feature.