Coda, D.S., and D.C.

[Cedar]

Codas and D.S.s ... Can you add them on the web editor?

Yes. The Coda and Segno signs are in the Rehearsal marks menu.
To make any text, use Staff text (near the dotted line across the chart.) You can move it up with the arrows if you want it at the top of the bar rather than along the bottom. Sometimes you have to start it in a beat a little before you think so it all fits in... for instance "D.S. al Coda" which is quite long.