Looked everywhere for this but can’t find it.
I know there is a button on the right side that increase/decrease/1:1 vertical zoom, but where are the buttons horizontal zoom?
The default keys are Ctrl+Up and Ctrl+Down.
You can also simply use your mousewheel if you have one.
PS. You can search key bindings in: Edit > Preferences > Keys
For example, you can simply enter the keyword “zoom” there to find all related keys.
doesn’t seem to work here (focus in sample editor).
2.8 seems to have no defaults? Or is that because I had changed my 2.7 keys to be Up/Down, which now moves you between left/left+right/right channel selections? Always worked fine (well my own shortcuts) in 2.7.2.
Are the key bindings actually mapped to anything?
If the sample editor has focus and the keys are mapped but not responding, then this is definitely weird and maybe a bug.
Not sure if anythings mapped, I’ve never changed the shortcuts, and as these are defaults, nothing should be changed?
That’s why I’m asking, mate 
If you do have the default mappings and they’re not working, then we need to know about it!
Could even be that your mappings got screwed somehow. It’s impossible to know anything for sure.
Don’t just speculate, take a look and find out what’s going on
Yeah, I checked real quick in the preferences, but couldn’t find the particular sample zooming choice quick enough in the list, so I quit and went pizza eating 
… if I put in ctrl+up in the new assignment window without having selected any current assignment, it doesn’t throw up any conflicts, so it isn’t mapped(?)…but I’m not sure this is a correct way to search for conflicts, maybe I should first select a current assignment?
errr, forget what I wrote, checked again and can find ‘zoom in’, ‘zoom out’ and nothing is mapped there.