I hardcoded size and position values in Sway to hide it outside the screen.

Here they are for 1366x768:

for_window [app_id="dev.zed.Zed"] floating enable, \
                                    resize set width 1387 px, \
                                    resize set height 830 px, \
                                    move position -15 -75


bindsym $mod+2 workspace number 2, \
    for_window [app_id="dev.zed.Zed"] floating enable, \
                                        resize set width 1387 px, \
                                        resize set height 810 px, \
                                        move position -8 -60

This won't work unless I keep Zed in workspace 2 though.

If I don't re-run the command when switching workspaces Zed changes position and breaks my hack. There should be a better solution to the workspace problem.

Edit: I know I input different values in both cases, but it doesn't work otherwise.