With Swing, it is possible to select some text in t:texpane (in order to copy the selection into the clipboard by clicking with ctrl-c.
Unfortunately, this is not possible now with RISC.
Could you make it possible?
As a possible workaround, I have tried the demo workpage "Setting/Getting clipboard Content" with RISC. But it seems not to work for Firefox. In Chrome and Edge, it is a bit cumbersome (a popup is shown with the text in order to copy it). It works "normal" only with the (obsolete) Internet Explorer.