Another nice trick with the slice tool is you can have the top and bottom of the slice be different places, and the slice will be the average of the two points. So if you ever need an extra half beat of hihat bleed or something it’s easy to do while still staying quantized.
Everyone talks about the piano roll being the highlight of FL studio, but for me it really is the mixer. I’ve tried other DAWs and giving up the ability to route any mixer track to any combination of other tracks is impossible for me at this point. I think that flexibility on full display in the mixer side is what makes it so complicated from the playlist side - which is where you will spend a lot of your time after you figure out the mostly intuitive piano roll but before you get to really play with the mixer.
The problem with the playlist is over the years it has tried to be all things to all people. It is the arrangment view where you stitch your patterns together into songs. Then they added live mode and it had to be able to function as a performance space similar to the grid system in ableton (but of course with greater flexibility, because you can put anything on any square, they aren’t pre organized into mixer tracks like ableton). Then they wanted to make it into a linear audio editor like Protools so they added the ability to turn each track into an audio track pre-routed to a mixer track with recording controls on every level. Oh, and also this is one of like 5 places you can work with automation data so it has to do that too.
I have found over the years that my biggest leaps in music have come from better and better understanding how to use the playlist. I’ll send you a screenshot of how I organize things later, but it takes up 2/3 of my screen pretty much all the time. Keep everything in there organized. I put one instrument to one track (say synth one in track one, synth 2 in track two, drums in track 3, etc). I then add automation directly below each instrument it affects (so drum automations, even if it takes 10 tracks, would be on the 10 tracks directly below drums) and if I have too many tracks to fit on my monitor, then I group the automations with the instrument/audio tracks and hide the automations that I’m not editing.
If you need a scratch area for audio editing and ideas, you can drop in a song marker that says “start” and give yourself a few bars of playlist to work with. The start marker is where your song will start rendering and where your play head resets to. Bonus, if you mark the various sections of your song (verses, bridges, tempo changes, etc) those markers will show up in the audio file when you import it into FL later, like leaving yourself helpful notes if you mix stems or master your work as a separate step. In a similar vein the fruity notebook plugin is great. I can leave myself notes of what I think the track needs at the end of a session so next time I jump back in (even if it’s months later) I can remember what I was going to do next.