Windows does not natively support this, but it is possible.
You will need to use a 2nd pc and use RDP, VNC, TeamViewer, etc... to connect to it. This desktop will then become one window that you can size and alt-tab to.
Alternatively, you can use a Virtual Machine, such as Oracle VirtualBox, install Windows into it, and run your applications in there. You can then alt-tab to that VM and view the windows like that. Running a VM does cost a lot of CPU usage, and is probably not what you want for a simple task as this.
Lastly, you can use Virtual Desktops to group windows together, and switching to a different Virtual Desktop will hide all but these windows. Windows 10 comes with its own Virtual Desktop manager, recognizable by the [
[_]]
icon in the taskbar next to the startmenu orb. If you Alt-Tab to one of the programs, it will show both. Alternatively you can WIN-CTRL-left or WIN-CTRL-right to navigate between desktops.
You may have to enable Virtual Desktops first. To do so, go to start
> Settings
>System
>Multi-tasking