Private islands, island levels, challenges and coop: describe the progression you want, get a compiled SkyBlock plugin as a .jar, and test it online first.
A SkyBlock plugin rests on four pieces: generating private islands, an island level scored from the blocks placed on it, challenges that give players a goal, and coop so friends can share one island. With Minax you describe your own progression in plain English and get a compiled .jar you can test online before installing.
If you want classic SkyBlock, an existing plugin does the job and you configure whatever its author decided to expose. If your level table, your challenges or your coop rules fall outside that, generating your own plugin is usually faster than fighting somebody else's config file.
No. You describe what your commands do, how the island level is scored and what challenges pay out. Minax writes the Java and returns a compiled .jar. The source stays yours, so if you can read code you can open it and change it.
The plugin reads the blocks on the island, applies a value to each one and sums them. Your value table drives the whole progression. If you do not provide one, a starting table gets written into the code and you can swap it for yours afterwards.