When formatting symbology (ArcGIS Pro 2.3.3) in the Symbology pane the 'Value' and 'Label' column widths will not stay fixed! For example, when I expand the 'Value' column width (so I can see the values!), then click on the symbol to format it, it goes to the 'Gallary' where I can choose a symbol. When I go back, the value field's width has defaulted back to 100 pixels-wide.
Obviously this is annoying when I have to format a lot of symbols. I have to keep expanding the column width every time I return back from the gallery.