I have trouble locating seeds; such as, pinto beans, great northern, etc.--- Currently. I save seeds from the year before but originally I bought bags of dried beans at the grocery store and planted them. I want to plant lentils this year but I don't have seeds. Has anyone planted lentils from the dried lentils in the grocery store?

Yes it is possible. You never know just how old the seed in the grocery store is, though. You might want to test first, take 10 or 20 seeds on a moistened napkin or paper towel and see if they sprout. If you get sufficient sprouting after a few days (I'd go up to a week), then I'd go for it. If not, then lentil soup.
A few order sites if you want to go with finding variety lentil seed specifically for growing:
https://www.saltspringseeds.co... (canadian)
https://www.anniesheirloomseed...

Concur: I have over the years bought pea and seeds from the supermarket, when I did not need to be variety specific. Have not had any germination problems, but I do patronize stores which turnover inventory rapidly. Lentils have crossed my mind a couple of times but never got around to trying them. Apparently there are differences between varieties. They are considered a cool weather crop with a long DTM. Wonder how they will handle our hot summers.