You can have a variety of similar topics, but you need to at least be mindful of what is happening when you do. The woodworking and leather work topics seem similar, but understand that when someone comes across a leatherwork video and they enjoy it enough to subscribe they found you because they needed something to do with leather. So when you post a leather video that is what they subscribed for and this is likely what they are going to watch. If you post a design program video that is going to be served to this viewer (either as a push notification or as a suggested video). They came to you for leather, and odds are they are not going to watch this. When YouTube serves video it reflects as an impression in your analytics and YouTube is watching to see how many people are clicking on it. So when you have a bunch of these viewers who came for leather and they are not clicking on your design program video YouTube doesn't know that this is a different video with a different audience. They simply see that this new video is not getting clicks. This drops your CTR, and the video will inevitably perform far worse than it would were it served to the audience that is actually looking for design program content.
It is important to have this laser-focus on your niche (at least at first) because it helps to build authority in that niche so that YouTube knows exactly who to share it out to. But also the response that you get from a less confused audience helps to bolster the performance of your videos. Once you have that foundation of viewers who have grown from enjoying what you do simply for your leatherwork to enjoying your personality then you can branch out a little more. But when you first start off it is better if you remain dedicated to a singular niche.