I’ve been knitting, crocheting, sewing, weaving, and most other things textile related for decades and have never come across this tool. I inherited a box of yarn and other crafting items that included this in a sealed bag with three small balls of yarn and a yarn needle. I have never seen one of these before. Can anyone tell me what it is?
That looks like a bone folder (aka paper creaser) to me. A plastic version though, not actual bone. I've got one that's similar in bright orange, although mine doesn't have the notch near the tip.
It definitely comes under 'other crafting items" rather than yarn related though. It should be blunt, because they're used for making creases in paper without puncturing it, so that the paper can be folded more easily. Think book binding, card making etc.
Honestly, I'm not surprised it showed up in a bunch of unrelated crafting stuff; they're slippery critters, prone to wandering off and reappearing somewhere else entirely.