I am watching the teaching videos online and cannot reproduce several things. One is that the histogram box in PSE Editor 2021won't expand so as to see all of the choices at the top of the box and it doesn't have the litle arrowheads at the far left and right to make any changes. Any help is appreciated.
The tone curve tab is missing in the ACR Elements version.
The idea in the selection of available tools for the 'consumer' version seems to be to skip features which are available in the pixel editor. You can open a 16 bits pixel version of your file in the editor and use the levels and curves tool. I have always recommended using black & white gradient maps adjustment layers in luminosity mode to fine tune custom curves. The interface is different, but the background calculation is identical.
Another reason about the lack of curves tab is that the editing process in ACR has evolved from the old school workflow based only on curves. The available tools to correct the tones of shadows/highlight with clarity work not only on curves, but also on local contrast, which is nearer to the way our brain 'correct' the tones. That's why I rarely need the curve tools in my workflow now. The 'basic' tab in PSE ACR has the 'fundamental' tools to edit faster and better.