Observation:
Somatic spell components require a free hand, but usability is not very good in that UI flow (->open inventory, unequip shield/off hand weapon, cast spell, next turn: reverse order).
You could argue that weapon configuration slots are for that, but that doesn't work well. Usually one is for melee, and one is for ranged. The third customization option is for light.
Suggestion:
-A button/shortcut to equip/unequip off-hand (game needs to remember the item that was unequipped)
-Or a 4th configuration slot, similar to the light preset, that is re-using the currently held 1h item. Specifically designed for "free off hand" config.
In this idea I made mistake. I forgot that people also do it the other way around: A free main hand, with a shield equipped to cast with the free main hand.
So that makes things a bit more complicated I guess.
Maybe the 4th slot could be configurable by the player, so that you can choose to keep main/off hand.
I enjoy the game much more with Somatic component off in settings.
I still need Material components and a spell Focus/Holy symbol, but I can just ignore the hand micro-management for casting (which I really tried to play with, but very tedious after over 30 hours).
Steam profile : https://steamcommunity.com/id/baraz/
Quick swapping weapon inventories unbalances the game in favour of combat classes. Stowing weapons requires an action in 5E. You are not supposed to be able to switch things out that quickly unless you drop stuff on the ground.
"Stowing weapons requires an action in 5E."
Repeating a lie won't make it true you know.
That aside, I plus the addition of equip/unequip off-hand... On the principle.
I do worry that it would be a real puzzle to solve for developers.
First, there is the specific case of shield which is the only item that explicely and exceptionnally require an action to equip or unequip since it's an item with special category of "armor". Would it be hard to distinguish it from normal use-case for devs? And how to make the distinction clear?
Second, the UI is kinda crowded as is, and there are also other legitimate (imo) suggestions on "action management" addition, notably "choice of weapon for Attack" for dual-wielders or Monks.
Maybe the best would be to simply wrap everything pertaining the Attack action inside a submenu like they did for Monk's bonus action "powers" (which should really include FoB even if I do get this was an arbitrary choice made on the assumption FoB would be the most often used option although that's not really true).
As for equip/unequip, maybe it would be worth magnifying a bit the current "short-hand set swap" and add afterwards a "boolean icon" representing either the sheating or the drawing of an off-hand weapon.