I am using HTML5 Help for output. We are finding that a lot of our users zoom their browsers above 100% which can cause the Table of Contents panel/sidebar panel to get collapsed. Is there a way that I can force that panel to keep its size and shrink the topic panel instead when a user zooms or resizes the browser window?
What's happening is that as they zoom, the "responsive" part of the Responsive HTML5 name kicks in. This is designed for using the help on phones and tablets, but also affects desktop browsers when you resize the browser window or zoom in.
Which version of robohelp are you using? If it's RH2020 you could try turning off the Responsive toggle in the skin you're using. However, if you need the help accessible on different size devices, then this probably won't be acceptable.
You could also try playing with the Phone and Tablet maximum width setting, but you'll need to test on a wide range of phones and tablets to make sure the experience is acceptable for those users. This is also the only option if you are using Classic (if you don't need phone or tablet if using classic, I *think* you can set both to zero, but don't quote me on that as I've never tried).