I spent the last few hours yesterday figuring out what tools I wanted and getting a general idea of what they should be capable of and what they might look like. By the end of the day I was mostly satisfied with what I had and would be ready to start implementing them the next day.
And so began the terrible slog that is trying to write GUI applications. Surprisingly it wasn't as terrible as I had anticipated this time. I ended up creating a small subset of a custom GUI library for myself that ended up being loosely based on the Immediate Mode GUI model. It still took quite a while though so at the end of the day I only have one tool actually completed. A tile and palette editor!
Not exactly the best tool ever made, but it works and it's better than my current workflow which is all that really matters. Hopefully having a small GUI framework written will make creating the rest of the toolset much quicker.