As per Wiktionary, the definition of "upvote" is the following
To vote for, increasing a cumulative tally of popularity.
Note that the phrase "a cumulative increase" in the above definition emphasizes/ denotes a "quantitive" change.
I was searching for synonyms for upvote and these are the closest alternative words/ phrases -
approve; agree
However, I believe that these words do not indicate a "quantifiable" increase
My question is the following -
Are there single word alternatives that incorporate the "quantitative/ cumulative increase" aspect of the word "upvote"