I suggest add an option to remember plugins states for each currently opened documents separately. And preferably I can config some plugins to remember it's state globally and others per document.

Suppose I am editing 3 documents (doc1, doc2, doc3) and only "Projects" plugin is configured to remember it's state globally. While doc1 is active, I turn on "Projects" plugin and "HTMLBar" plugin. Then I activate doc2, "Projects" plugin will be remain ON as I configured it to remember state gloabally. But the "HTMLBar" plugin will be OFF as I haven't turn it on for doc2.

If I then turn on "WebPreview" plugin when doc2 is active. The states of plugins for each documents will be:
doc1: Projects=ON, HTMLBar=ON, others=OFF
doc2: Projects=ON, WebPreview=ON, others=OFF
doc3: Projects=ON, others=OFF