In theory, you can enable the caps lock by double-touching on the caps up-arrow. In practice, you have to double-touch really, really, fast. This usually doesn't work for me.
If you touch the up-arrow once to go to single-caps mode, the icon turns blue. If you touch it again in that mode, it goes back to lower case (the icon is grey). If I try to double-touch it, but don't do it fast enough, then Andriod thinks that was two separate touches and I wind up back in lower case mode.
What seems to work reliably for me is to touch once to go from lower case to upper case, and then long-touch to go into caps-lock mode. A single long-touch from the lower case mode won't work.
The bug is that there is absolutely no visual difference between single-cap, and caps-lock modes!

I've seen posts here and elsewhere saying that in caps-lock mode the arrow icon changes color from blue to white, but it doesn't on my tablet. It stays blue.