So just a couple of suggestions on the new deck builder:
1) Would you be able to add cell outlines to the card database? I have larger monitors (27" and 24") and it can be hard to track line information across that distance. I think giving the database a more spreadsheet-like appearance would help with that.
2) Would it be possible to make the columns in the card database have an adjustable width? Again, I have larger monitors and it can be hard to track one line instance across half the monitor.
3) This one is more of a personal nitpick, but would you be able to add in the ability to create new sections in the actual deck builder? Not the subsections, which are fine, I just don't like having my custom headers under the control of the "Main" section.
And the last one 4) Would you be able to replicate the subsection creation under the maybeboard? I think it would greatly help in organizing the cards people are thinking about putting into their decks.