Beginner code completion questions

I just installed a trial of CLion, to use for C++, and I'm playing around with code completion. I have a couple questions. 

One of the repetitive things I type are `using` declarations at the top of a file. For example `using std::cout`, `using std::vector`, `using std::chrono_literals`. I don't like typing "::" (it's worse on my Dvorak layout).  I notice that... 

#include <iostream>
using ve       // shows std::vector completion at top of list
using cou      // no std::cout
using sc       // show some matches on std::chrono by matching the first letters
               // but again, no std::cout

Is this controlled by a setting somewhere? Is it a bug?

I notice that there is some support for splitting the string and matching the initial letters of parts. For example: (parens show which letters are highlighted as matching)...

using sc     // shows list with (s)td::(c)hrono::steady_clock 
             //                 (s)td::(c)hrono::system_clock

But if then try to keep typing to select one of of those, it doesn't work. Say I type "scsy", to try to narrow that down to "std::chrono::system_clock". It doesn't find anything. Even "scs" doesn't match anything. It seems like if "sc" matches "std::chrono", then "scs" should match "std::chrono::system_clock".  

Oddly, "using ss" shows a completion list for "(s)td::chrono::(s)ys_seconds. So in that case it did start matching on the 3rd part. ?? Is there an explanation somewhere of how this works? Is this configurable? Is it a bug?

thanks,
Rob

CLion 2022.2.1. macOS 12.5.1