Hey I'm new here, but here's how to get lots of Dcoins in a long grind if you don't have Version 1.15.0.
1. Head to language level in puss mode.
2. head straight to the A rooms. (turn left from elevator hall, then head straight to from the 3 paths, you will find about 7 doors once your there with each door being a tiny white room)
3. In the 5th door to the left, you will find 3 Dcoins.
4. Rinse and repeat.
The amount you get at the end of your grind will depend on how fast the level loads for you and how fast you do the process, so for everyone it will vary. For me I estimate that i got 100 coins every 15-20 minutes doing this process. For some it will be faster and for some it will be slower. Have fun being board.
P.S. I know That FireyDeath4 had posted V 1.15.0, but it doesn't work for me and i lose my belt data so all my artifacts are gone