Sometimes in my career, I was faced with the need to draw scientific schemes for presentations and works. For a long time, I used tools such as BioRender which is indeed a great tool for those who are not used to draw.
The point is that using these tools allow you to easily do nice figures that improve your work, but as time goes on you begin to feel limited and stuck.
It happened to me and I decided to learn how to draw my things. I tried drawing in PowerPoint, Inkscape and lately in adobe illustrator. These are very good software that allows you to draw a lot of things. They have their characteristics and you should take a look into each one of them before deciding which one to focus on.
(I get used to the adobe illustrator, which has a pretty friendly interface and is intuitive, but all the three may meet your requirements)
Take a look at the main options:
How do I start learning?
Initially, I made some schemes in PowerPoint and they met what I needed at that time. However, some things are not so easy to do or, at least, not so intuitive in PowerPoint. Then I tried Inkscape and adobe illustrator and choose adobe illustrator as the one I was focusing on.
Learning something new may sometimes be tricky. I would suggest you test all the basic tools of the available software first. Then there are a lot of tutorials on youtube that will teach you how to make specific drawings. This is how I started and, of course, which worked for me.
One such video tutorial that explains the basic properties and tools of adobe illustrations is here:
Once you get used to the interface and the basic tools and want to start drawing scientific objects, I strongly recommend you to watch and follow the DrawBiomed channel on youtube.
This channel is run by Jon (Jon Jieh-hen Tsung), which is the founder of DrawBiomed. There you will find a lot of videos teaching how to draw a lot of things, such as receptors and DNA strands and, ultimately, graphical abstracts.
There you will find videos teaching how to draw objects in Inkscape, PowerPoint and adobe illustrator. One such video that I like and that was one of the first I watched was the following: