A couple of additional questions would be:-
1/ I like the format in JRemote 2 where each listing has the track name, then the album and then the artist. This is important as I have many tracks which have multiple versions and multiple artists which I need to ID before selecting the track. Is there a way to achieve this also into Gizmo and my musiccast app??
Gizmo is an old application and is unlikely to see any further development. Use JRemote2, as it is in development now, and will continue to get better.
How your Musiccast App displays information is entirely up to Yamaha. MC provides information about the tracks via DLNA, but what the App does with that information is out of JRiver's control.
2/ The grouping feature helps to simplify searches by reducing the options but it would be much better if within each group you could do a keyword search to go straight to what you are looking for. Does JRiver offer this functionality?? If keyword search within groups is not possible is it possible to improve the existing search function in gizmo and jriver which I have found only work in some positions in the tree, don't sort results alphabetically and, below track names often don't give the artist and album also.
If you go into a Group in JRemote2, for example "G-I", then search using the magnifying glass at the top of the screen, JRemote2 will search within that group. But the search only uses track names at this time. That will improve in the future, so I'm told.
Gizmo only has the search function on the Home page. It is a global search based on all media on the MC Server Gizmo is connected to. Searches using expressions are supposed to work, and I have used them successfully in the past I believe, but a quick expression based search I did just now didn't give me the result I wanted. i.e. I used the expression "[Genre]=rock", but that didn't work. Just searching for "rock" gave me several options to select from, so that works.
That is the limit of the search options at the moment, as I understand them.
The third party App, "MO 4Media" has different search capabilities, which some find much better.
I am not sure if you are a MC developer but if you are I hope you can take a very serious look at this as, given I have 35,000 tracks I see a good search tool as an absolute necessity.
I'm just a user like you. I'm looking forward to better search capabilities in JRemote2 myself. It will come.