I’m going to show you how to fix a problem that’s driven me crazy literally for years.
If you’re using KRDC to remotely access a computer with VNC, the Scale button, by default, does nothing.
It’s actually a super easy and kind of silly fix. If you prefer video, see my YouTube video on this embedded at the bottom.

If you look at the KRDC config file you can see that scaling defaults to 100.

For some reason, this causes the scaling button to do nothing.
To fix this, you could hand edit the krdc config file every time you have a new connection, or, you can just add the Scaling Factor action to the toolbar.

Go Settings then Configure Toolbars

Scroll down and select Scaling Factor
Click the right arrow to add it to the toolbar
Click the up arrow to put it next to Scale
Click OK

If you click Scale, still nothing happens.
Turn Scale on and then drag the slider and scaling will start working!

At this point you won’t have to drag the slider anymore.
Once scale is off of its default value, the scale button works as expected. Simply do this for every new VNC client you connect to.

If you prefer video, follow along here: