You can insert the custom code by page in Step 3 -> Page Editor (Pencil Symbol), click "Source" tab on under toolbar.
As WYSIWYG is the 3rd party plugin into RVSitebuilder program, so the keyboard control will not take effect to event of "tools" in the toolbar.
Let's say that:
1. In Source view, if you use keyboard control for "Ctrl+c" to copy, you'll need to use keyboard control "Ctrl+v" to paste the content.
The same way when you want to delete all content at once, to delete by keyboard. You'll need to copy all content by "Ctrl+a", then use keyboard "Delete". This will take effect on removing all content at once.
If you use mouse hover and "Select All", the keyboard will not take effect at all.
2. If you use mouse hover and use "Copy" tool in the toolbar or "Select All" by right click, you'll need to use "Paste" icon in the toolbar or "Paste" from option right click to paste. The 'Ctrl+V" will not work this way.