User needs to use modification keys (control/shift/alt/option) to change between 'info', 'horizontal' and 'vertical' modes on the heatmap.
Right click on a square gives the context menu, but the options depend on the mode.
Desired scenario:
Moving accross the heatmap reveals a cross (see below)
Clicking on a square displays an info box with additional information on the square.
Right click on the square gives the context menu with all posibilities for square/rows/columns
Dragging the square:
The first direction of the drag does not matter (in case someone moves one pixel to the direction they don't want to go).
Once the drag moves to a column on the left or right, the drag is locked in vertical mode, and the selected can be dragged and dropped to the desired position (without changing the rows).
Once the drag moves a row up or down, the drag is locked in horizontal mode
Current scenario:
Desired scenario: