Note how only the "ToggleItemFlag" and the "PrevReadItem" line have defined key bindings, while "NewVFolder" and "SearchMenu" don't.
To change a key binding first remove the semicolon at the start of the line and then adapt or clear the key binding field. Choose prefixes like "<Primary>" (for Ctrl), "<Alt>", "$lt;Shift> as needed and append the key after it.
Variant #2: Enable Editable Accelerators with your Linux Distro Settings
This variant is hard to document as different distributions have different setting dialogs. Some expose a setting to enable life editing of key bindings. Once this is enabled you can open a menu hover over a menu option and press the accelerator you want to assign. It should show up instantly.