TL;DR
When the player character is in a vehicle and selects an entity with inventory, allow transferring directly between the vehicle and entity.What?
There might be alternate ways to do this, but when the player is in a vehicle and clicks something like a chest, instead of always showing the character inventory on the left, allow toggling between the character and vehicle inventory. Allow the standard inventory management methods, such as control-clicking a blank slot to transfer the entire inventory, to allow items to be transferred without going via the character inventory as an intermediary.Rough mockup:
Why?
Dumping the vehicle inventory into a chest, or the other way around, is frequently not straightforward:- If there are multiple types of item in one or the other, it can be hard to keep track of which items in the character inventory are meant to be transferred on to the final destination, especially when "always keep player's main inventory sorted" is enabled.
- If the character inventory doesn't have sufficient room, the transfer might need to be done in multiple small steps, or else the player may need to make room in their inventory by storing the contents in a temporary crate (or several).
- Inserters are a less manual transfer method, but can be very slow.
For simplicity, construction and deconstruction while in a vehicle probably should continue to only use the character inventory.