Isn’t that basically the “Ignore” option? You can ignore an item so that it is never tested on until you un-ignore it.
I’m not sure if this is relevant, but there is also the “individual auto learn” option
You can see it on the top right
Imagine this scenario:
You are learning a level which has both words you do know and ones you do not know. However, you don’t want to ignore them, but at the same time you don’t want to waste time learning them again. In this case, you just press the auto learn button (or keyboard shortcut) and the word will be auto-learned as if you spent 5 tests on it and you will not be tested on it for the remainder of the session.
However this option is disabled by default and you have to enable it from the settings.
This is only available during a planting session though (I.E. when learning an item for the first time). It is not visible during watering (review) because during watering you only need to answer it once anyways. But if you don’t want to be tested on it, you can just ignore it. Ignoring a word will not delete your progress on it.