So, I understand the design reason behind it being a permanent slot rather then a temporary storage.
Since the forge interface can be opened while interacting with the world and moving, hence not auto-closing when your character moves or interacts with something it demands that it stays inside.
The reason is simple as well, imagine you walking around the world and picking up an item which takes up the space formerly filled by the item you’re crafting currently. This leads to an issue.
What should be done?
We can’t put the item back into the space it formerly belonged after all, it’s now filled, we can only do something else.
The most likely result would be that the item instead drops on the ground… which since it can be done in a monolith or general gameplay leads to one issue… you could be killed during it. That would be a big ‘oof’ since that item is after all one you decided is valuable enough to be crafted, which not every item in your inventory might be at the time, hence it’s likely the most valuable non-equipped item you possess.
A chance of loss? That’s not good.
So instead it is made a permanent storage slot so those situations can’t happen. Replacing the item newly put in would also be bad as that one suddenly drops on the ground, all in all ‘a bit of a mess’ hence. All of that shouldn’t happen.
So the solution which could be made is to do something similar like PoE does.
The second any input designed as creating a character action, hence moving, picking up items, attacking… all of that automatically closes the UI, inventory and enforced the position of your item to be put back into the space it has formerly been in.
This also demands that now all other items can’t be moved in your inventory though. Imagine a ring being displaced during your time crafting and now taking up the space of your chest armor, leaving no space to put it once again.
Next issue.
So since the forge UI itself is a separate entity which puts the item in the only realistic way to solve this issue is by making it a temporary space, removing the item from the inventory and putting it into it not causing it to actually ‘move’ but instead - as player feedback - being ‘ghosted out’, it becomes transparent while being ‘placed’ - just a representation - into the forge UI.
This way it isn’t actually moved and no problems related to character interactions can happen as it just ‘snaps back’ into place as soon as you do.
This still demands that character interactions are set as a natural trigger for that window though.
In the end it comes down to a lot of work for very little upside. Definitely an improvement I can agree to but a boatload of work for sure. So while probably taken into consideration and on the list of work for EHG it’ll be quiiiiiite low on the list.