In order to use formatting on mobile app also, then please use the markdown editor instead of the standard editor in
Notezilla app for Windows.
Go to
Notezilla app on Windows, right click inside the sticky note and choose "Switch to Markdown editor".
Double click inside the sticky note to edit the note. Then you can press Ctrl+K to strike the text. There is also Formatting toolbar that you can show at the bottom of the sticky note. Right click inside the sticky note while editing, and choose "Formatting" to show the formatting toolbar for more formatting options.
Once you are done formatting, you can press Escape key to go back to read mode.
After which, when the note syncs with the phone, you will see the formatted text on phone too.