well, good questions, our previous discussion of how to show meld cards was helpful and I commented I will possibly add some of that later.
There is only one live player in Rating, the rest bots, so that sometimes makes a difference with some of these issues versus for example what marya has to handle, but for declaring meld there is only a number input. There is no specifying what the meld components are, if I did I would have to list them without numeric values and have them both checked off and still the meld amount entry. Actually, displaying meld types would be a type of cheat and not real life as would be used as a checklist.
So would checking off cards and somehow indicating which are part of what meld group without providing a meld checklist helpful to provide some more real life experience to the game? I don't think so. To count the meld you have to recognuze Kings Around and add the meld for it as you would at a table. I can't see the phsical act of clicking on four Kings really all that compelling.
So, a meld amount is entered. If greater than your actual meld, the program displays an error and allows re-entry. It's sort of like sitting at a table. if you lay meld cards down and say a higher number than it is, opposing team will correct you.

For that matter, meld is often counted by the scorekeeper when you lay it down, certainly double checked. There's no renege involved in declaring meld that I ever saw.
Now technically a player could start at some high number and reduce the meld amount each entry until it was accepted as a cheat mechanism without really being able to identify the meld very well and correctly. I have an error count on any kind of error and if there are repeated errors I basically suspend the game and provide a login page. My assumption being a persistent communications error but handles repeated errors whatever the reason.
When melding is completed, I display meld for each player. That is done with text such as Aces Around /n Double Pinochle /n etc without showing ieach meld component value but showing a meld total. I don't know, if a player can't see why it's totalling up different than they expected they can look up the meld values.

Experienced players I would think wouldn't want to see every hand what Kings Around etc are worth I would think. But of course I will provide a link that will show meld values anytime, while they're counting, when it's displayed, whatever.
That's how it works (and has always worked for the DOS game back in the day). I did find the discussion on preferred meld display pattern we had with marya to be interesting and as a lower priority it would definitely be more realistic to display the cards as well. When I get to that point I'll take a look at how you guys are doing it.
thanks for the interesting questions, mick. You can call me rd if you want.