Randomized Voluntary Study of Previous Content?

You guys are probably looking for this userscript
[Userscript] Self-Study Quiz

It does exactly this. I would like to include a fair warning that studying items right before they’re up for review is kind of cheating because you’re not letting yourself truly be tested on the longer timeframe (but there’s a setting to not quiz items coming up soon anyway).

I know you guys are low level and may not have started grammar yet, but there are videos like this playlist on youtube that I would also recommend for reinforcing vocab, and seeing vocab “in the wild” is excellent for self-study.