Two devices into one monitor

It won't work if you want to use the HDMI port on the Mac mini.

For the features and web cam to work, the connection must be done through a thunderbolt port as HDMi does not work for data or bidirectionally. It's just a video output and nothing more.

You can simply have 2 thunderbolt cables one to each computer and switch the one connected to the display when required, or just unplug the TB cabled from the MacBook Air and plug it into the Mac mini as required, or look for a thunderbolt KVM switch that can let you switch between the Macs with a button or switch.

TB KVM switches are rather expensive though.

There are Keyboard-Video-Mouse (KVM) switches available, both locally-wired and remote network-connected.

There are monitors with multiple inputs, and some with integrated KVMs.

There are keyboards that can also switch the Bluetooth or wired path as well, though the Apple keyboards don’t have that feature.

The wrinkle here is going to be the webcam, as most KVMs of my acquaintance don’t have a port for that. How that connects and how that might (or might not) switch?

Thunderbolt KVMs are comparatively not cheap.

The BenQ model you list doesn’t match any model I can find, but it is close to the PD3225U model, and the PD3225U model does apparently have an integrated KVM:

https://www.benq.com/en-us/monitor/professional/pd3225u.html

I have not used and am not familiar with the BenQ KVM feature.

More BenQ KVM info:

• https://www.benq.com/en-us/campaign/monitor-for-mac/articles/one-set-to-control-two-systems-with-kvm.html
• https://www.youtube.com/watch?v=XznXvR1G3Cw

Check the BenQ docs for your particular monitor for details.

Your Benq PD3225U monitor has two HDMI 2.0 ports on it. Amazon has several choices of 4K HDMI 2-into-1 splitters with remote control switching. You connect both computers to this device via HDMI with one HDMI cable out to your Benq. This allows you to easily switch your HDMI signal without fiddling with the display controls.

If you knew that you would be upgrading to a 4K/120 Hz display in the future, then this splitter might be of interest. Otherwise, that Benq monitor only supports 4K UHD/60Hz, and this Anker 4 in 1 out might be useful. Amazon has plenty of choices for this type of device, and Anker is simply an example device. For any HDMI switching solution, read the fine print about HDMI 2.0+ cable length restrictions.

Although I have considered a 2 in 1 out HDMI splitter for my configuration here, I have deferred doing so as my M4 Mac Mini is the primary device, and my 16-inch MacBook Pro increasingly spends more time in the backpack than on my desk.

I had a monitor well 3 monitors really

the first had an xbox, a mac mini, work windows laptop and desktop connected to it by various forms of hdmi and thunderbolt adaptors to dvi, hdmi, subD(analogue) adaptors and switched between them using the buttons on the monitors. and logitechs mx series let one connect between 3 and 4 devices at the same time one can swich between, was never worth it for me to look toward normal KVMs