As far as I remember, in H14 it used to be that when you right-click on an HDA and select “save node type”, the HDA would save all changes and turn blue.

Now in H15 I am creating HDAs (with the .hdalc extension) and the “save node type” option seems to do nothing at all.
Is this intentional? Is there an option to get the old behavior?

Save Node Type just saves the changes to hda definition, but keeps the asset unlocked (red)
if you want to lock the asset and sync with definition saved to disk you need to do Match Current Definition afterwards

or you can use Asset Menu where those options are Save Asset and Lock Asset respectively

Well that is my issue:
Save Node Type does not save the changes to the hda definition. And I have this issue on two different computers. I feel like I'm doing something wrong, or this is some kind of bug.

I assume you're looking at another asset, and the new changes are not showing up there? It's possible that your other asset nodes are unlocked. When an asset node is unlocked, the node will have its own changes, and won't update from the HDA file. If that's the case, you should be able to lock it back by right clicking the asset, and select “Match Current Definition”.

I can't see an issue with RMB + Save Node Type

if this isn't saving the current state of your hda, please check that you are saving to the right location…

I feel really stupid now, but it's still not working. So here's what I tried to do:
1. Create digital asset.
2. Delete it and re-create it from TAB menu (to try and work with it, like I would in a different file)
3. RMB -> Allow editing of contents.
4. Edit stuff inside the HDA
5. RMB -> Save node Type
6. Create the Digital Asset from Tab menu -> It does not have any of the changes from step 4.
Alternative:
5b. RMB -> Type properties , click apply and accept
6. Create the Digital Asset from Tab menu -> New asset has changes from step 5b

Note: When I do step 3, it always becomes “Not synchronized with definition”. But how else can I change the HDA?

So what am I missing?

The delete step is something I had issues with before,

after you delete it, instead of tab creating it, use “install asset library” so houdini knows where it is coming from again

@MikePaixao
Tried that, it didn't work. Also tried making a new scene and installing the HDA there. That didn't work either.

What happens if you have 2 houdinis open and you make an hda in one, does putting it into the other houdini show your changes?

Again, the only thing that works is:

RMB -> Type properties , click apply and accept

But the proper method (RMB -> Save node Type) does nothing. I will try updating to a newer daily build in the weekend.

This is pretty strange. Which Houdini 15.0 build are you using? Which OS are you on? Since you mentioned you're saving to .hdalc extension, I assume you're running Houdini Indie?

I was running 15.0.297 Indie. I am now trying 15.0.307 and it seems to work fine.
Thanks for trying to help me solve this, everyone.