Currently, anything normally stackable, that is differentiated by .nbt (Treated Wood tables with contents as example) can be duplicated by placing such an item with contents in the grid/storage of these tables, and shift-clicking any number of others into the same stack.
Checked across multiple versions of the Mod for 1.14.4, as well as 1.15.2

Alright, thanks for that hint! Just in case you wanna laugh a bit: I had to fix that also for the Hopper, both Furnaces, the Milker, the Waste Incinerator, and the Dropper ;-). Porting Item equality glitch.

Alright, the fix is approved on curse. Could you double check and close the issue if it's okay on your setup? Cheers -

Thanks much!