First off, you should double-check check you are using all the features of your pellet grill/smoker to increase smoke production. Some people don't realise that sometimes their pellet grills have a dedicated smoke setting to boost smoke production, such as Super Smoke on Traegers and Smoke Boost on Weber pellet grills.

The second thing I would point out is that all pellet grills will produce most of their smoke between their lowest temperature setting and 275 degrees. The reason is, in that scenario, there is a smaller pellet fire, and a smaller fire is less efficient and produces more smoke.

If you still need a smoke boost, your final option is adding in an additional smoke box/smoking tube, which you can place on the cooking grates next to the food you're smoking. Consider the direction of air/smoke travel through the cooking chamber on your pellet grill/smoker and carefully place the smoking tube/box accordingly.