Just need to know if something is possible... (Simple)

Is it possible to make a mod where, when a player upgrades a certain stat, I also give them a bit of another stat?
Upgrading crafting speed is nearly useless, so I want when the player upgrades it not only do they get +10 crafting speed but also +5 health

it is likely possible if you mod the player pawns or whatever holds those values. Have it check for changes and apply new changes. For example on play it grabs the stats and stores them in variables, then on tick or a custom loop it checks current stats against the saved ones, when one is changed it then runs a pathway that adds to another stat as well and sets the two stats that were altered back to the reference variable which would then do nothing until one of the stats changed again.

You could also likely do this with a buff. Have an object that gets placed that gives all players in the world a buff from the server side, that buff then monitors the players stats and makes changes to the stats in the same basic way. This way is a bit more work but offers a cleaner stackable option.