Run Synergy Software KvM as Admin if You Screen Capture
I used to use a set of bulky cables to run two PCs from a single keyboard, mouse and monitor when monitors and laptops were expensive. Once I had multiple monitors running video from laptops I found a software that does the keyboard and mouse sharing via TCP/IP (internet) and I gave up on the cables.
There are free and commercial KvM utilities, I use one called Synergy. (I use a small v in KvM since it doesn’t really do anything with video but we still use the old term.) It is commercial, although you can use an old version for free with no support. That version is the one I started, so I have never upgraded and it still works fine. It also allowed me to use my MacBook Pro as a second monitor for my PC. They have a video about how it works. That old free version has a very confusing setup and UI: if you are just getting started, spring for the commercial version.
One thing I noticed recently after installing it on a new laptop is that Synergy would stop working whenever I ran a screen or video capture utility, such as Snagit, Camtasia, Jing or even Windows Snipping Tool. Not only that, it would seem to get the alt, ctrl and shift keys stuck as if they were pressed down, and this would persist after I had stopped capturing. This would prevent saving screen captures and generally any interaction through the keyboard got hosed – very frustrating! For a while I tolerated this by using my laptop keyboard and trackpad during captures and then tapping the alt, shift and ctrl keys repeatedly on both laptop and main keyboards to reset things. (And then tell Windows “No I don’t want to turn on Sticky Keys – argh!”)
The correct solution to this is the always run Synergy as Administrator on the system where you are capturing- it will retain control of the keyboard and mouse during all capture sessions that way. If you don’t have admin rights, you probably can’t install and run a software KvM in the first place.