Thank you Uli, follow up below-

On Fri, Jul 10, 2020, 2:52 AM Ulrich Sibiller <uli42@gmx.de> wrote:
On Thu, Jul 9, 2020 at 10:54 PM Jonah Benton <jonah@jonah.com> wrote:
>
> Hi folks,
>
> I'm interested in using x2go to:
>
> * connect into several individual accounts/machines at the same time
> * use each remote machine desktop in full screen mode
> * switch between remote full screen desktops using a specific key combination, which would therefore not be sent to the remote
>
> Is this possible?
>
> In my initial perusal of man pages and testing I don't see a way to do what seems to me to be the (probably wrong) solution- instruct the x2go-client (in either launch remote desktop mode, or desktop screen sharing mode) to not capture a specific key combination (like control-alt-right arrow and control-alt-left arrow) so that the parent desktop can handle them (e.g. switch between parent-side virtual desktops).

Well, switching between application windows is a task of your local
window manager or, more precisely, its task switching app. The reason
you cannot do this in fullscreen sessions is that a session running in
fullscreen mode will grab the X server to get ALL keys. That means no
other application will get notified of keypresses. The hotkeys
("keystrokes") will be processed by the nxagent and will not reach the
session. All others will be forwarded to the session. We could add
another keystroke, something like "passthrough" or similar to pass
that keystroke to your local X server. But even then I doubt that
would work at all because usually grabbing prevents such things from
happening. The only other options was to explicitly disable the grab
in fullscreen mode which will probably lead to making your local
session unusable because a window that is covered by the x2go
fullscreen needs some interaction but cannot be activated or similar.

A more pragmatic approach: do not run in fullscreen but use maximized
windows instead. Then your local window manager/task switcher will
happily fullfill your request to switch to another x2go session.

Uli


The explanation is very helpful and it along with running some experiments has clarified the mental model and convinced me of the futility of my imagined approach. Events are pushed to the client window without grab, but are pulled by the window with grab, acted on or not, and discarded. 

So re using maximized windows- the grab behavior allows for key combinations like alt-tab, or copy paste, that are present both locally and remotely to be only processed remotely. 

In the absence of grab, can I still achieve the ergonomics of working natively in the remote environment, as with alt-tab? For keys, would I need to bind each needed key combination in the remote environment to a key combination unused in the local environment? Or maybe only alt-tab and shift-alt-tab? 

Or is there an "ungrab" but leave full screen, then "regrab" when necessary?

Thanks again, appreciate the insight-

Jonah