This feature is available in some other DAWs, such as Steinberg's.
I often find myself in need of automating parameters in sections of my arrangement, but want those parameters not be automated during the rest of the arrangement.
That way, I can use re-enable automation, and have only those parameters respond which I want automated for that particular section.
Since automation locks a parameter to a certain value for the entire arrangement, even if only a short section is automated, this takes away a key component of freedom when performing with a combination of manual control and automation.
- Max