Previously you could duplicate seeds with croptopia (which was broken obviously) and get a lot of seeds very fast, but after the update (because right-click harvest from croptopia has been disabled) you can't get a secondary seed at all.
I have tried for a while to get a secondary seed from an essence farmland but I had no success with the same tier essence farmland nor with the supremium farmland. I believe the secondary seed drop is disabled in the config file (which can be enabled if you play on singleplayer but if you have no access to your server providers FTP then you have no chance of changing on the setting in multiplayer) and with the croptopia fix, the Mystical agriculture is unplayable if you are not willing to spend MASSIVE resources into creating new seeds one-by-one by the altar, and if that is the case then you are better of just running a quarry and the mod has no use.

No need to close, it'll happen automatically when the code gets added for next release. Thanks for bringing this to our attention