How to simplify combat operations and directly select weapons to start an attack?

Assuming I understand what you're going for,
I would just make abilities named "Sword" "Dagger" etc and put Use conditions on them for has equipment type sword equipped, and use the matching icons

"Weapons" from the player perspective is all UI anyways.. icon and tooltip and equipment menu or shortcut, so ability isn't much different.

Also the equipment itself is not really an attack in Ork

You can make the weapons override the base attacks so that depending on weapon equipped the base attack changes automatically

Beside overriding base attacks, equipment can also grant abilities (see the Equipment Abilities settings of the equipment).

So, instead of the use conditions on abilities, just have the equipment give that ability while it's equipped.

I want to switch weapons and attacks to be instantaneous, that is, switch weapons in the battle menu and attack immediately

I have implemented the above process through a custom EquipmentBattleMenuItem

public override void AddToMenu(ref List< BMItem> list, Combatant owner, BattleMenu bm, BattleMenuItem parent)
{
UIButtonInputContent content = bm.contentLayout.GetContent(this.button.GetContent());
this.customInput.Use(content);

List< EquipmentSlot> slots = owner.Equipment.GetAvailableSlots(this.onlyContributing);
for (int i = 0; i < slots.Count; i++)
{
EquipmentSlot slot = slots[i];
if (slot.Equipped == false)
continue;

List< EquipShortcut> equips =
owner.Inventory.Equipment.GetByEquipmentSlot(slot.Settings);
this.contentSorter.Sort(owner, ref equips);

if (! slot.Settings.hidden &&
(! slot.IsBlocked || BlockedSlotDisplayType.Hidden ! = this.blockedSlotDisplay) &&
(! slot.IsLinked || BlockedSlotDisplayType.Hidden ! = this.linkedSlotDisplay))
{
for (int j = 0; j < equips.Count; j++)
{
var equipShortcut = equips[j];

var slotBMItem = new CustomEquipmentSlotBMItem(this.GetChoiceContent(owner, equipShortcut), slot.Settings, this, parent, equipShortcut);


list.Add(slotBMItem);
}
}
}
}