Please add the above option - I believe this warrants a UI pref, but dconf at least, as the current behaviour has some serious drawbacks as the only option.

The current behavious of suspending/unsuspending VMs when backgrounded means, among other things, that:

* Background tasks cannot be run in one VM while interacting with another.
* Switching between VMs varies between slow and very slow, because of the heavy IO involved in suspending/unsuspending.

Right now the only way to manage multiple VMs without suspending all but one, is to use the 'open in a new window' option, and then keep a separate window open for every VM all the time.

Switching to a second VM without suspending the first is very unintuitive with this approach - you have to 'open in new window' the current VM, then switch back to the previous window, which then shows the other VMs, and you can then open the next one - not an obvious mechanism at all.

Please also make it possible for disabling of VM suspension to apply to closing Boxes as well.

A variation might be to prompt for suspension on 'back' and close actions, with 'this time' and 'always' options, with a relevant pref in the UI.