Can you provide a picture or a plan? I'm not following the description at all.

A picture out of your sliding door and one back at the house will help. More pictures are better. And what zone or location.

Have you thought about elevated planters for the side to grow food? If you are not in a zone that would tolerate, maybe a putting green or a place for corn holes?

There are some really great ideas to share but we need to know more about your home first.

How much do you enjoy gardening - plants, flowers, veggies? What climate are you in? What kind of light does the side space get?

Do you have enough outdoor space for relaxation and sitting? Do you need any kind of storage on the side of the house for outdoor equipment?

How many people live in your house and who - does anyone want or need a separate outdoor space for a hammock, reading, a rock garden, a water feature, a pergola with a hanging bench swing, firewood storage, an enclosure for trash cans or mechanicals?

My apologies, I thought my pictures had loaded into my initial comment. Here are three pics. This is a Northern California property. And I'm no green thumb or gardener, so while I might not mind putting a box or two on the ground or fence for maybe herbs, that would be about the extent of my interest in that. It seems like a lot of videos tell you to make something for the dog or a golf/putt-putt which I'm not too keen about either. This lot gets nearly full time sun on the side yard, and some shading in the back early morning, and late afternoons when the sun starts to set.

It looks like you have a blank canvas. I would say do what speaks to you. Reading into your comments, it seems like you have already put much thought into what you don't want, but I am not sure what are your top priorities or any potential wants.

When we redid our backyard, we put different sections such as lounge sections, dining section, and workout area. We really wanted a nice fire pit, a permanent outdoor ping pong (we host a lot of backyard bbqs), and plenty of seating. We also put in pergola, tv, inground speakers for music (we use this way more than I would have thought) and some fruit trees.

Some kind of inspro

Please plant a couple of trees. You won't regret it. Look for something labelled columnar or fastigiate - both indicate that the tree will be narrow and grow more upwards rather than outwards. Even if you did nothing else out there other than mulch under the trees, you and your neighbors will benefit from shade, screening, greenery and breaking up the expanse of stucco walls. Plus the birds will appreciate it as well.

Depending on where you are located in Northern California, your hardiness zone could be anything from 6 to 10. If you can provide the nearest large city, you may get more specific plant recommendations.

Storage shed and pad for gear and equipment in the side yard. You don't say what your interests or needs are. A patio for seating and an umbrella would be nice in the backyard.