Double duration

.

See (if I understand well, no sure?)
https://musescore.org/en/handbook/4/copy-and-paste#half-double
If not, please precise things (eg with an image)

I would call a "double duration eighth note" a quarter note.

Or do you mean double duration dots? If so take a look at the last paragraph of https://musescore.org/en/handbook/4/entering-notes-and-rests#selecting-… (immediately before the Note).