I changed my tilemap layout to default to the full-size map window. In fact I'm going to remove the resizable option altogether.
when showing the data window, it will resize to a smaller map with split map/data window so that they're both visible at all times.
the reason for this is when placing a data tile, like a legend that has data that's editable, then it paints the tile with blank data (unless using the data brush, where it paints whatever data is preset into the tile).
if the data is blank, that's not going to render anything, but then choose the selection brush with the data window open, so then it's possible to set the fields and such.