If you are missing fonts that you were able to use before in the offline creator tool for Windows, you can follow the steps below to make them visible again.
1. Go to the "File" tab.
2. Click on "Settings".
3. Uncheck the checkbox "Show only TrueType fonts for text editing".
Please note: if you have a lot of fonts installed, unchecking this box can make the editor respond slower than usual.
Were you previously working from another device and downloaded additional fonts? You will need to transfer them over. See continue working on my book on another device for further details.