This is the how the Custom Study menu looks in Ankidroid:
Here, the same dialog in desktop:
One of the most common questions I see in the forums, specially from newcomers, is how to study a few random cards from a deck. Ankidroid offers a quick an easy way for that, but in the Desktop version is not so easy to find that option, you have to click in the last option, choose “All cards in random order”, click on “Choose tags” and then choose tags to include / exclude even if there are not tags in that deck.
Since Custom Study menu is primarily designed as a set of quick presets for filtered decks (more advanced users often use the Tool > Create Filtered Deck option directly), I would suggest, for the sake of use, to just add that option to the main Custom Study menu: