What the "Attack/Save: Wisdom" wording is trying to do is say whether the ability is an attack OR a save. E.g., If it's an attack, it would say "Attack/Save: Attack". So you're interpreting the category listing ("Attack/Save:") as the tag, whereas in reality the tag is "Wisdom" meaning the enemy makes a Wisdom Save.

But yes, this can obviously be confusing.

+1 for removing the category listing ("Attack/Save:") and just having the word "Attack" if it's an attack or "[ability] Saving Throw" if it requires an enemy ST. Possibly include modifiers such as "ranged or melee" and/or "spell." And the tutorial needs to be improved to better explain the rules of 5e.
Originally Posted by Niathlak
Attack/Save: Wisdom

Obviously this means the save will be based on their spell save dc + wisdom modifier, if im not wrong about that..
This is incorrect, depending on what you mean by "their spell save dc." When you cast Saving Throw Spells, the enemy has to beat your spell save dc (8 + proficiency + [caster ability score modifier]), ~always calculated using the ability score associated with your class - intelligence in the Arcane Trickster's case. The enemy makes a saving throw: 1d20 + [ability modifier dependent on the spell] + [proficiency in that save if they have it] and compares it to your spell save DC.

So yes they add their wisdom modifier, but they add it to 1d20 (possibly + proficiency bonus) instead of their save DC.