When creating a multiclass spell-caster, you learn and prepare your spells as dictated by your class as if you were only that class, so, as a 5th-level artificer and 6th-level wizard I learn and prepare my artificer and wizard spell based on if I was only a 5th and/or 6th-level artificer and wizard right? Does that override the fact that wizards and artificers can both learn and prepare spells based on if they have the spell slots to cast them? For instance, as a 5th-level artificer and 6th-level wizard I have up to 5th-level spell slots, so let's say I run across a random 5th-level wizard spell and want to learn it, I'm technically only a 6th-level wizard, but I have 5th-level spell slots from my multiclass, and as stated by the wizard class, I can learn or copy spells into my spell book upon leveling up or finding them as long as I have the spell-slots to cast them, so can I or can't I learn these spells.
If I can, then dndbeyound's character creation tools' doesn't account for this, as I can not add such spells to my spellbook as it does not show up in the character creator or the spell manager on the character sheet. The same goes for artificers as they have a similar description of how they can prepare their spells, saying they can prepare their artificer spells as long as they have the spell slot to cast it.
Now if the previous is true then when you take a level in spellcaster maters, Let me refer back to the previous example, as a level 11 character, 5 levels in artificer and 6 in wizard, I have up to 5th-level spell slots, now let's say I decide to multiclass after I've already taken all 5 of my levels in artificer, the first level of wizards says that my spellbook only has 6 1st level spells in it, but on the next level, I learn two new spells, these spells being spells for which I have a spell slot to cast, as a level 5 artificer and level 2 wizard, that would mean my highest spell slot would be 3rd level, does that mean I can take a spell like haste as a level 2 wizard? What if I reverse the previous example, what if I level up in turns between wizard and artificer?
I don't believe dndBeyound accurately portals these character and gameplay choices as far as I can tell, If it does could someone point it out to me?
You can learn spells as a wizard based on the wizard progression table and the spell slots it expects you to have in that progression, not accounting for any multiclassing. Otherwise, it would be trivial for a wizard to take 19 levels in wizard and one in cleric and have full access to both spell lists, as a simple example of one problematic use case. The text in the class descriptions doesn't account for the theoretically optional multiclassing rule, which is the cause of your confusion here. The designers have clarified their intent since the printing of the PHB, and so DDB developed their spellcasting tracking software to follow that intent.
When creating a multiclass spell-caster, you learn and prepare your spells as dictated by your class as if you were only that class, so, as a 5th-level artificer and 6th-level wizard I learn and prepare my artificer and wizard spell based on if I was only a 5th and/or 6th-level artificer and wizard right? Does that override the fact that wizards and artificers can both learn and prepare spells based on if they have the spell slots to cast them? For instance, as a 5th-level artificer and 6th-level wizard I have up to 5th-level spell slots, so let's say I run across a random 5th-level wizard spell and want to learn it, I'm technically only a 6th-level wizard, but I have 5th-level spell slots from my multiclass, and as stated by the wizard class, I can learn or copy spells into my spell book upon leveling up or finding them as long as I have the spell-slots to cast them, so can I or can't I learn these spells.
If I can, then dndbeyound's character creation tools' doesn't account for this, as I can not add such spells to my spellbook as it does not show up in the character creator or the spell manager on the character sheet. The same goes for artificers as they have a similar description of how they can prepare their spells, saying they can prepare their artificer spells as long as they have the spell slot to cast it.
Now if the previous is true then when you take a level in spellcaster maters, Let me refer back to the previous example, as a level 11 character, 5 levels in artificer and 6 in wizard, I have up to 5th-level spell slots, now let's say I decide to multiclass after I've already taken all 5 of my levels in artificer, the first level of wizards says that my spellbook only has 6 1st level spells in it, but on the next level, I learn two new spells, these spells being spells for which I have a spell slot to cast, as a level 5 artificer and level 2 wizard, that would mean my highest spell slot would be 3rd level, does that mean I can take a spell like haste as a level 2 wizard? What if I reverse the previous example, what if I level up in turns between wizard and artificer?
I don't believe dndBeyound accurately portals these character and gameplay choices as far as I can tell, If it does could someone point it out to me?
You can learn spells as a wizard based on the wizard progression table and the spell slots it expects you to have in that progression, not accounting for any multiclassing. Otherwise, it would be trivial for a wizard to take 19 levels in wizard and one in cleric and have full access to both spell lists, as a simple example of one problematic use case. The text in the class descriptions doesn't account for the theoretically optional multiclassing rule, which is the cause of your confusion here. The designers have clarified their intent since the printing of the PHB, and so DDB developed their spellcasting tracking software to follow that intent.
In short, D&DBeyond does it right.
Partway through the quest for absolute truth.
Thank you for the clarification.