It will be great, especially for modders. It's often needed to see NBT while modding.

This is actually already part of the mod, but disabled in the code. Will be looking into adding this as a full feature for the next update though.

Thank you. ATM in my mod i display NBT in tooltips, but not correctly, i have some troubles with NBTTagList (trying to show all tags apart, not just using toString() method in this class). So i will very happy to see this feature in WAWLA.

It only took me nearly 2 years to add this lol. With the way Waila/Hwyla works it's actually really costly to do nbt stuff because it needs to be synced to the client. I added partial support for this for entities, however I am not syncing any additional data. I am planning to implement a better version of this feature in my debug mod Caliper, which will not require syncing to the client directly with Waila.

To activate the new debug mode, you have to be in creative mode, with advanced tooltips (f3 + h) on.