There is no officially published list of people whom the US considers worthy of swaps.
But there is a law (the Robert Levinson Hostage Recovery and Hostage-Taking Accountability Act) that gives the basis for the US State Department to review cases and assign them "wrongfully detained" status. The Secretary of State is supposed to make a determination based on the "totality of the circumstances" based on an 11-point criteria. The list of those criteria is pretty long and while some are rather clear by US standards, e.g. freedom of speech etc., others less so like "being detained solely or substantially to influence United States Government policy or to secure economic or political concessions from the United States Government". Griner was granted that status by the State Department in May.
The State Department doesn't like discussing (some of) the cases in public much. E.g. rather simultaneously with Griner, Marc Fogel was sentenced to 14 years in prison also for drug smuggling into Russia. He had been arrested in 2021. He was given this longer sentence supposedly for "large scale" smuggling, although according to himself he only had 17 grams of cannabis, while the Russian law supposedly only allows that "large scale" label for >100 grams (according to the Western press). Insofar it does not appear the State Department has given Fogel the "wrongfully detained" status.
There is a statutory requirement for the State Department to submit an annual report to Congress on such findings, but as far as I can tell, they are only required to submit (any) details for the cases in which the Department does make such a (positive) determination, as opposed to all cases considered for review. (Insofar I wasn't able to find a sample/such report, but the law was only adopted in 2020.)
It's somewhat difficult to find out when others who were swapped already (like Trevor Reed--detained in 2019, swapped this year) were granted the "wrongfully detained" status. (I know he was granted this status, based on his swap announcement, which clearly indicates that, but it's not clear to me how long it took in that case. Reed had also been sentenced to 9 years, and according to himself it was the longest such sentence ever handed out for that type of crime in Russia.) That presser on Reed's swap, from the end of April only mentioned Paul Whelan by name as another "wrongfully detained U.S. citizen", presumably with the additional criterion being also in Russia. (Griner had not yet been granted the "wrongfully detained" status by the State Department; that came a few days later in May.) Whelan had been detained on espionage charges since 2018 and sentenced to 16 years in Russian prison.
(The US State department also labels countries with a "D" label in its travel advisories, when it deems that countries are likely to wrongfully detain Americans. Russia currently has that label as do other countries.)