I had mysterious, unselectable text in my document with multiple columns. It turned out to be a table, but this was not indicated anywhere in the UI. Not in the layer list or the Properties pane when the text frame was selected. Table properties are missing from the Properties pane even when you have the text-insertion point sitting in a table cell.

A major contributor to the problem is that the tiny table-selection icon that appears on the left side of a table has no ToolTip, and does nothing when clicked or dragged. Only by guessing that you have to double-click it will you discover that this invokes row/column selection mode. And only then do table-related controls appear in the Properties pane.

I would expect a ToolTip on the on-screen control, and I would expect table properties to appear in the Properties pane when you have the insertion point in the table.

InDesign 20.2 on Windows 11.