@vertus01
Unfortunately, not possible in "true" Opera. This feature was one of the most requested by users. But Desktop Team had ignored this suggestion.

My Opera 12 usually have a lot of opened tabs. So, the start(restart) of the browser could be really annoying.

I am using special batch(.cmd) file that starts Opera in "lite mode" that radically reduces Opera's start up delay.

The batch file simply asks me:

Do you want to disable javascript in Opera? Yes/Cancel. Do you want to disable plugins? Yes/Cancel. Do you want to disable images? Yes/Cancel. Do you want to enable Offline mode ("Work offline")? Yes/Cancel.

For an example, with disabled JS and images, Opera starts much faster with a much less intensive CPU workload.

Also, i have the custom buttons(made by me) in my Opera toolbar config. The buttons allow me to enable JS/Plugins, disable Offline mode, enable(load) images in all opened tabs in a quick way.