Since I created my sidebar lists when I was still using the old version of blogger, they are all written in HTML. The strike out command is also done in HTML language. It looks like this
49. <>PINS Churn Dash Exchange < /s ><>DONE!< /strong >
Update: In the above example there is supposed to be a letter "s" inside the first set of brackets. I've tried to correct this several times, and every time I save it the "s" disappears.
The <> is placed directly before the first word you are crossing out, and the < /s > is placed directly after the last word you are crossing out. The second command is very important - if you forget it then everything after will be crossed out.
Important note: In my examples above and below I had to put a space before and after the command in the brackets in order for the command to remain in a form that allows you to see the HTML. When you type it there are NO spaces inside the two brackets.
You may also notice these two commands above: < strong > and < /strong >. This is what changes the font to BOLD. I don't know very much HTML, but have fun using the small amount I do know.
Note: the word "strong" should be between the first set of brackets in the second HTML command. Like the "s", it keeps disappearing.
If your sidebar list is created using the "List Gadget" instead of the "HTML Gadget" then I have no idea how to strike through items on the list.