Amongst blockchain’s challenges, which term refers to how many more Tx the blockchain can accomodate?

The term that refers to how many more transactions (Tx) a blockchain can accommodate is typically called "scalability." Blockchain scalability is a measure of a blockchain's capacity to handle an increasing number of transactions or users while maintaining performance and efficiency. It's an important challenge in the blockchain space as networks need to scale to meet the demands of a growing user base and increasing transaction volumes.

[Answer is scalability]