The rule on Bonus Action Casting Time states:
A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven’t already taken a bonus action this turn. You can’t cast another spell during the same turn, except for a cantrip with a casting time of 1 action.
This would ordinarily prevent you from casting a levelled spell and a bonus action spell on the same turn; however, the Artificer’s Spell-Storing Item states:
[…] While holding the object, a creature can take an action to produce the spell’s effect from it, using your spellcasting ability modifier. […]
Furthermore, the following question’s highest-scoring answer states:
- Do class or subclass features that relate to spellcasting apply when producing a spell's effect from an Artificer's Spell-Storing Item?
[…] The user never casts the spell either. They merely use a (special, unnamed) action to produce the spell’s effects. They don’t cast it and don’t get to modify it with their features which care about them casting a spell. […]
And the Sage Advice Compendium even states (page 3):
Q. Which action is used to activate a Spell-Storing Item?
A. Activating a Spell-Storing Item uses the Use an Object action.
Does this mean that a caster could use a Spell-Storing Item, creating the effects of any 1st or 2nd level Artificer spell with a casting time of 1 action, and then use their bonus action to cast any (bonus action) spell?