You can save the WiFi password in the disposable template like this:
You can remove disposable sys-net qube and create a non-disposable sys-net qube instead:
- Rename sys-net to sys-net-disp
- Create a non-disposable sys-net
- Change the sys-net-disp to sys-net everywhere in Qubes Global Config and the in the Settings for all qubes that have sys-net-disp as net qube
- Remove sys-net-disp
I’m not sure what do you mean by not having the Network Manager. Do you not see the Network Manager applet icon in the system tray?