In our last session the party was ambushed by kobolds, and I included a trio of kobold scale sorcerers, a monster I have not used before.
The scale sorcerers have the ability Heightened Spell, which is nearly identical to the Sorcerer PC metamagic ability:
When it casts a spell that forces a creature to make a saving throw to resist the spell's effects, the kobold can spend 3 sorcery points to give one target of the spell disadvantage on its first saving throw against the spell.
However, looking at the scale sorcerer's spell list, of eight spells known, there are only two that would force a saving throw against the spell: poison spray and charm person, but either of them is unlikely to be used during a combat with PCs. Further, the scale sorcerer has only 3 sorcery points, and it would need to use all of them on a heightened spell, so the particular single-use should be one of consequence; far more so then disadvantage on the save against a single use of the poison spray cantrip from a sorcerer that for some reason has entered melee range. Forcing disadvantage on a charm person save would be a great use of heightened spell if cast as part of a social interaction instead of a fight or even after a fight (when the captured sorcerer is negotiating to be spared or released), but again the sorcerer is unlikely to try charm during a fight.
On the other hand, the scale sorcerer has three spells that require attack rolls and do damage: firebolt, chromatic orb, and scorching ray. I believe that tactically, these spells are far more likely to be used in combat against PCs, especially when considering that they synergize with the sorcerer's Pack Tactics ability. These spells do not force saves directly. However, if cast against a PC caster with a Concentration spell going, their resultant damage would force a Constitution save to maintain concentration, and spending the single-use Heightened Spell ability to give disadvantage on that save (if it was possible) seems like the tactical best-use scenario for the ability.
So, looking again at the Heightened Spell description, would a damage-dealing spell that forces a Constitution save to maintain Concentration be "a spell that forces a creature to make a saving throw to resist the spell's effects"?
I have checked the 136 instances of "effects" in the PHB and as far as I can tell, there is no game definition of what "spell effects" are, just a lot of contextual references. Thus, "effects" should be interpreted with its 'natural English' meaning of "consequences".
A restrictive approach might be to say that "spell effects" are limited to those specifically listed in the spell description itself; damage is a spell effect, but the Constitution save is an effect of the damage, not an effect of the spell. Further, the Heightened Spell description says that the disadvantage is "on its first saving throw against the spell" itself, not against the spell's effects.
A permissive approach might be to say that "spell effects" include all mechanistic consequences of the spell. The spell creates damage and the damage forces a save without any choice or "may" conditions intervening, so the Constitution concentration save is an effect of the damage-dealing spell. Further, had the Heightened Spell description been written to specifically exclude such consequences, it needn't have included the word 'effects' at all, and would just have said
When it casts a spell that forces a creature to make a saving throw, the kobold can spend 3 sorcery points to give one target of the spell disadvantage on its first saving throw against the spell.
So, Can the scale sorcerer use their ability to allow it to force disadvantage on the Concentration that result from damage-dealing spells?