I am Running Cura 3.6 appimage on Linux Mint 18.3 (Ubuntu Xenial)
I just learned about support blockers and Per Model settings.
Woohoo!
That lasted for about a minute.
Although, looking at the layers it seemed to work just fine. I thought I would walk you through how I finally had to do it. The GUI wasn't any help at all.
Here is what happened:
Added Support blocks where I wanted them. Good so far.
Then I tried to do the per model settings on one of those blocks. And that's where the GUI wierdness came in.
1. select block.
2. click per model settings
3. select modify settings for overlap with other models
4. select modify and settings window comes up, and select infill density
5. value box appears, and I can't click in the change box. No way. Period.
5.1 (Then I close the main select settings window) and the value box is still up, and NOW I can change the value
5.2 I change it from the normal value to 100, and hit the enter key. I don't really know if it is changed or not. So I hit the escape key.
6. Then I do a prepare and show layers and indeed it is different.
So it all appears to work, but what wierdness in the GUI.
I was able to repeat it for all the support blocks.
So it all works, just not cleanly, IMHO.
Jerry