The toggle would default to on, turning off for only a single attack when you click it, and then automatically turning back on. So in the 90+% of cases where you'd want to sneak attack on your first (possibly only) attack each turn, it'd require no extra clicks. In the remaining cases, it's almost a certainty that you'd want to sneak attack on your 2nd attack, so it's still only a total of 1 extra click.
I shouldn't have been so categorical; your explanation makes sense. In case a 1 hp foe is standing next to the rogue, that is quite helpful (I'm not being sarcastic, it happens more than I thought it might).
A few counterpoints:
1. The current system already has this benefit (or very close to it). If you're worried about wasting your sneak attack on a low hp enemy, just start off with your off hand attack. I'm almost certain that this maximizes expected damage anyway, so the toggle doesn't present a strategic edge in that regard.
2. It would be the only opt-out toggle... Wait, that's not true. Bardic Inspiration is mostly off/partly on. And I couldn't say whether Great Weapon Master is on or off by default.
3. Speaking of GWM, a toggle would be compatible with attacks of opportunity; the current system isn't.
...
Ok, I can see how a Sneak Attack toggle could work. However, I'm not a fan of the toggle system working in quirky, inconsistent ways. Sneak Attack would be the only toggle to switch positions without direct player input. Given how diligent Larian are about explaining their game systems, that might be too ambitious.
Best to resverve judgement for patch 9. Just four weeks to go...
