Hey there,
when you select the instrument on the channel (tap) (blue triangle indicates Library focus), or the Inst is loaded on a channel, 
the instrument library will be listed on your left as you already know, you can see the folder 'Factory' in Library when you do so and then do the same menu tracing as above to find the sounds you're after.
Also you could find your favourite sounds without having to open menu after menu by using the "Save As" as or "Save as a copy" from the Instrument menu, to a new folder (you'll need to create it to save your favs ), (button at the bottom left of the save as pop up window will give you that option). I do that when I edit sounds and save them with an initial or something specific, to differentiate from the original, I wouldn't really recommend saving the same sound but if it works for you.... additionally, search doesn't work for categories in Library which is not really great.

The favs folder or whatever name you'd like to give it ,will be available in the first column and you can create as many folders as you like for your fav sounds f.e. depending on their category...be aware that with years you'll end up with many of those that will be difficult to remember unless you organise them well.
You could also create Patches to save not only your fav instr sound but additional settings and plug-ins for channels and with 3rd party instruments etc
Logic Pro User Guide is searchable and easy to find more info about Patches.
A