[1st] Add Custom CSS
[data-rem-tags~="strikethrough"] .rem-text .highlight-color--red {
background-color: unset;
color: ;
border-bottom: ;
text-decoration:line-through;
text-decoration-style: double;
}
set color whatever you want.
In my case I sacrifice red highlight for the sake of Strikethrough
[2nd] Make custom tag : strikethrough
[3rd] Highlight text you want to strikethrough
the sequence is no meaning.
If there are something to fix, please let me know
Cheers!