One of the biggest parts of the Minecraft community has always been modders, and Minecraft’s Creator Tools have been aiding creators of parkour and adventure maps for a long time with customizable entities. That said, there is a whole rework coming with the Caves & Cliffs update.
One of the coolest things about the update is that all the types of changes you could apply to entities can now also apply to items and blocks. Before, mods like these had no in-game integration system, but now new blocks, textures, and effects can be fully integrated into a map in the same way entities are.
It will be the same system too, so modders who have worked with entities in the past will already be familiar with how to build, mix, and match effects. You can even cue actions during ticks of growth or decay of items like plants, or maybe blocks like the new copper as well.
Another great feature being added to the creator tools is Item Lock. If you are in an adventure map and you need to collect important items like keys or gemstones that you accidentally drop, therefore preventing you from completing the map, then the creator can choose to lock that item to your inventory.
A red triangle will appear on the item and tell you that this item cannot be dropped or removed until you reach the location where you use it, such as an interactive pedestal or door.
Overall, the new creator tools are adding new integrations and features that will make being a creator more exciting and open-ended and less frustrating, so why not give making some custom maps a try?