Most basses do NOT have the knobs marked. There is usually a plastic overlay on the pickguard when you first get it and it will often have them marked. Remove the overlay and you remove the knob index. Some will have a sticker next to each knob to identify what it does. If the manufacturer includes a manual, they should be noted in there. But sometimes they are not at all.
I got a Rogue 5-string years ago and they had included a hang tag off the volume identifying the knobs and their function. The functions didn't seem to correlate with the knobs they specified though and in some cases the knobs didn't do anything at all.
Well, come to find out, the bass and treble boost/cut knobs ONLY work when the bass is in Active mode. The bass will play in both active and passive modes. No where was that written and no one who sold it knew that. Found it on You tube on day.
So if I'm in passive mode, I can turn the bottom two knobs all I want and it won't make any difference in the sound. In passive mode, only the volume and pickup blend knobs (top two knobs) work. I usually use it in passive mode and all I am doing is adjusting the blend of the two pickups. If I find myself needing more than that, I just put it in active mode and then I can boost and cut bass and treble from there.
To make matters worse, the knobs on my 5-string don't even have an index mark on them. They have center detentes, but that's it. I may replace them some day with knobs that have an index mark along the top of the knob so I can see at a glance where I am.