Some of the more "obscure" drawing apps offer this sort of feature. These do, and in personal order of preference // with commentary:
ibisPaint // Funky, dated UI hiding VERY good performance and features. Good use of pressure in Pencil, too.
MediBang Paint // Busy UI, but ENORMOUS feature list. Incredible Power, like a desktop app on an iPad.
Concepts // Odd UI, but highly performant, and vector scaling of lines, plus excellent manipulation of selections, and duplicates
Sketchbook (Pro) // Has a dated UI for iOS, was one of the earlier drawing apps, but does have some of the best pens/pencils, still.
Procreate // Most famous painting app on iOS by a MILE!... but you will have to duplicate layers to get the ability you want, not select objects and copy/paste style duplication.
Pixelmator // same as above, you'll need to duplicate layers