Created few cards with a tag. The tag is not listed when try to custom study the tag-marked cards. Not sure how to solve.
Generally that happens when none of the cards in your selected deck have that tag (i.e. come from notes with that tag). Are you sure you’re looking in the right deck?
If you can find the cards by tag in the Browse window, you can skip the “Custom Study” settings and just build your Filtered Deck directly from the menu – Edit > Create Filtered Deck.