I often work with large files containing hundreds of variables. It's difficult to tell which variables are created vs. part of the underlying data file. I know that there's a color difference (black vs. grey), but this isn't easy to see, and the variables are all mixed up together. Please add a filter drop-down to the top of the Data Sources pane to allow the view to only show the type of variables selected in the filter. Examples of things to filter for:

Variables created in Displayr vs. source data file.

Variables that are completely unused in any context.

Variables that have "Usable as a filter" checked.

Variables that have "Usable as a weight" checked.

etc.