Every now and then I get myself a tray of party cheeses, crackers, and other party snack foods like summer sausage bites. You can prep it yourself for much cheaper, if you have the energy (you don't need to put them on party plates, you can eat your cubed cheese right out of the baggy you're storing them in!), and it's got the benefit of feeling like snacks instead of a full meal. You don't have to worry about finishing your plate if you never had one :P
Really takes the stress off of making sure you're getting those calories! I'm often hungry but too tired or cognitive dysfunctional to actually go make food, but snacks like that have brought my weight up to GREATNESS :P
One of my favorite ones is pigs in a blanket. You use cocktail sausages wrapped up in Pillsbury cresant dough (did i spell that right?). Usually two cans dough per one pack of Hillsboro cocktail sausages. Take an unrolled cresant directly out of the can and cut it into three triangles (it's already a triangle

so it's not too difficult). Wrap each sausage in dough (just roll it up) and then bake using the temp and time on the dough cans. Extra dough can be rolled up into mini croissants (OH THAT'S THE SPELLING), which you can fill with cream cheese (sugared if you want) and top with butter and cinnamon. They don't take long and if you eat all the sausages, you'll be set lol
Am even lazier one that works with my narcolepsy -- Tyson dinosaur chicken nuggets and those little microwave instant potato cups. For the potatoes, prepare with whole milk or cream instead of water and add butter. (If you're lactose intolerant like me, i usually take 6 lactase supplements with this one.)
Low appetite isn't the same as low energy, but sometimes you can trick yourself into eating these "appetizers and snacks" instead of a meal and it works regardless.
And i second the drink making with Greek yogurt. Icelandic yogurt, skyr, was invented to keep people alive in insanely cold winter temps. It's very thick and amazing by itself, but put that stuff into a blender or drink mixer or whatever with some cream or half-and-half along with blueberries, a touch of maple, bananas, cherries, and its GREAT. i like to make pumpkin or apple pie spice (cloves, allspice, nutmeg, cinnamon, ground ginger, hopefully not forgetting one right now but I might be) and speinkle it into anything I make to add excitement.
I'm now 150lbs instead of 100lbs after about 2 years -- you can do it too!
ETA: POTATO SALAD and also bean salads!! They come in glass jars and can be soooo hecking good. Pistachios. Mixed nuts (without or with peanuts). Just be careful on the nuts, because they contain lots of phosphorus and you'll drop your calcium intake a bit if you eat them with your calcium rich foods. Though those sargento balanced breaks have the right idea too -- cheese cubes with dried fruit and nuts are amazing snacky things that are easy to munch at. Just, especially if you're an older woman, consider adding calcium back into your body later. And make sure you're getting vitamin D because you need it to properly absorb calcium. :)
Cheesy eggs -- just scramble some eggs and add shredded cheddar to it when it's done cooking. (I suggest cheddar because those probiotics are also helpful.)
You gain energy as you gain the weight you need, so it gets easier to make things later