Does a level 13 Thieft that have the feature Use Magic Device can export this feature to other archetype? For example, Im going to multiclass to the artificier class. Would 'Use Magic Device' would allow my thieft/artificier to copy spell scroll without any restriction at all?
By 13th level, you have learned enough about the workings of magic that you can improvise the use of items even when they are not intended for you. You ignore all class, race, and level requirements on the use of magic items.
You are able to use any spell scroll that you come across. Scribing a scroll is a different mechanic, though. You aren't using a magic item, you are crafting one.
Regardless, Scribing a spell scroll has the following restriction:
Moreover, the character must have the spell prepared, or it must be among the character’s known spells, in order to scribe a scroll of that spell.
This restriction is not a class, race, or level requirement, so it is not ignored.
Actually, Spell Scrolls can only be used by a character who has the spell the scroll contains on their spell list. As you noted the Theif's Use Magic Device feature allows you to ignore class, race, and level requirements of a magic item. This has no interaction with the spell list requirement of Spell Scrolls.
Right but I as a 13th lvl thief/3 lvl wizard. Cannot learn off a spell scroll that has a priest only spell on it. I can use that scroll and CAST off it but I cant copy it into my spell book.
Actually, Spell Scrolls can only be used by a character who has the spell the scroll contains on their spell list. As you noted the Theif's Use Magic Device feature allows you to ignore class, race, and level requirements of a magic item. This has no interaction with the spell list requirement of Spell Scrolls.
Does the Thief’s Use Magic Device feature allow them to use spell scrolls? Yes. The intent is that a Thief can use spell scrolls with Use Magic Device.
I can see some ambiguity in interpreting the feature, but "the spell being on your class's spell list" can absolutely be interpreted as a 'class requirement'. And since that's the intent of the feature listed in the official SAC, that is the proper interpretation.
Right but I as a 13th lvl thief/3 lvl wizard. Cannot learn off a spell scroll that has a priest only spell on it. I can use that scroll and CAST off it but I cant copy it into my spell book.
Correct, because copying a scroll into your spellbook is a class feature of the wizard, and not a function of the magic item. Therefore, you cannot ignore the requirements of the wizard's class feature, which only allows you to copy wizard spells of an appropriate level.
Does a level 13 Thieft that have the feature Use Magic Device can export this feature to other archetype? For example, Im going to multiclass to the artificier class. Would 'Use Magic Device' would allow my thieft/artificier to copy spell scroll without any restriction at all?
By 13th level, you have learned enough about the workings of magic that you can improvise the use of items even when they are not intended for you. You ignore all class, race, and level requirements on the use of magic items.
You are able to use any spell scroll that you come across. Scribing a scroll is a different mechanic, though. You aren't using a magic item, you are crafting one.
Regardless, Scribing a spell scroll has the following restriction:
This restriction is not a class, race, or level requirement, so it is not ignored.
Actually, Spell Scrolls can only be used by a character who has the spell the scroll contains on their spell list. As you noted the Theif's Use Magic Device feature allows you to ignore class, race, and level requirements of a magic item. This has no interaction with the spell list requirement of Spell Scrolls.
Right but I as a 13th lvl thief/3 lvl wizard. Cannot learn off a spell scroll that has a priest only spell on it. I can use that scroll and CAST off it but I cant copy it into my spell book.
From the SAC: https://media.wizards.com/2020/dnd/downloads/SA-Compendium.pdf#page=6
I can see some ambiguity in interpreting the feature, but "the spell being on your class's spell list" can absolutely be interpreted as a 'class requirement'. And since that's the intent of the feature listed in the official SAC, that is the proper interpretation.
Correct, because copying a scroll into your spellbook is a class feature of the wizard, and not a function of the magic item. Therefore, you cannot ignore the requirements of the wizard's class feature, which only allows you to copy wizard spells of an appropriate level.