I have limited table knowledge in InDesign. Is there any to decrease the number of columns in a few selected rows, all while still keeping the original number of columns throughout the rest of the table? Inserted is a screenshot of what I am trying to accomplish. Right now, I have just placed 3 white boxes and text boxes ON TOP of the table that I wish to edit.
you could select cell 2 to 4 (as shown in your screenshot) in row 4 (the first one with your overlays) and merge the cells.
To select the three cells:
1. Put your text cursor in the first cell that should be merged
2. Hit ESC on the keyboard, that would select the cell, not its contents.
3. Hold the SHIFT key and then use the RIGHT arrow key to select the next one right to it.
Do that two times so that three cells are selected.
Now go to the "Table" menu and chose "Merge Cells". That will create one cell out of the three ones selected.