Baldur's Gate 3 doesn't really have an encumbrance system. It has a "send to camp" button that basically negates 99% of that. Camp supplies? Send to camp. Bunch of valueable loot items you only intend on selling "pick up and add to wares" the "send to camp". When you're ready to sell things between adventuring shove it all in a backpack, give it to someone stronk, and teleport to a merchant.