Is there any way to paste content onto an animated layer? I tried pasting then merging but that
erases the animated frames.

1. Paste to new layer
2. Select pasted layer, go to timeline and right-click the frame where you want the pasted layer to go, select "Copy frame"
3. If the pasted layer is going into a completely new frame then right-click on the frame where pasted layer will be merged to and select "New frame"
4. Right click the first frame of the pasted layer, select "Remove" frame
5. Merge

Quite tedious to do at the moment, hopefully will improve in the future. Specially since merging two layers clears their show in timeline flag.

Thanks Yoyobuae that did the trick! Tedious is right, that's so awkward but your workaround at least allows me to get it done.