The description of the monk's class feature Diamond Soul says the following:
Beginning at 14th level, your mastery of ki grants you proficiency in all saving throws.
Additionally, whenever you make a saving throw and fail, you can spend 1 ki point to reroll it and take the second result.
Does the Diamond Soul feature allow you to apply your proficiency bonus to your death saving throws?
Normally you're only able to gain proficiency in saving throws that have an ability score associated with them, and thus are unable to apply them to death saving throws, but this ability explicitly says that you gain it with "all saving throws".