You can as already mentioned use the arrangement to build songs in the OT and as others have mentioned it can be a little fiddly, a note pad or spreadsheet can help here to plan things since you don’t really get an overview.
However there are a couple of other ways, the first is to forget about the arranger and just have a bunch of patterns and perform your song by building, muting, tweaking and switching patterns manually (this is how I tend to work with it) It can be very inspiring working like this and you are free from any preset structure, if you mess up just redo it, it will probably be a bit different each time, and you can comp your best bits together in the DAW after if you want to.
Another way is to use a combination of the arranger and performing it live, you can set up all the parts in your song as sections in the arranger and manually switch to them as you feel by using the infinite loop section function along with REM to easily identify each section. Since the arranger can do some fairly interesting things like scenes, offset and reps you can even build little ‘ear candy’ fills that can be handy when you want a lot to happen but don’t have enough hands.
Finally you could use any external midi sequencer that has linear recording to capture all the moves you make on the OT (pattern changes, mute states, control data etc) It takes a little setting up but offers the “best of both worlds” in that you can just jam away then if needed edit the midi data to correct any mistakes, but could become a bit too much like what you are looking to avoid.
The thing with the Octatrack as has been said time and time again is that it offers a lot of ways to work and play - more so than anything else I have ever used in 30 years aside from perhaps a DAW, but it isn’t a DAW and can do some things a DAW can’t easily do, however all this flexibility comes at the cost of fully immersing your time into both learning it and learning what you want to do with it. For example I definitely think of it as a performance instrument, which it is, but like any instrument it takes time to get where you want to be with it, but it is also much more than that.
Still, I don’t really recommend the OT because of its flexibility and lack of instant gratification but rather I recommend that people watch as many youtube videos of people using it, then make their own decisions if it is worth the investment in time any money, whilst hopefully learning a bit from the many tutorials at the same time. To me it is absolutely worth learning, I would say get a mkII if you do decide to take the plunge as the extra buttons make things a bit easier.
Octatrack is beast mode