Any weight, especially if confined to small footprints will indent a carpet. This will occur more easily on damp carpet following cleaning, the plastic tabs won't make any difference. If in doubt place at the edge of the room rather than in a more noticeable area. A foot stool can usually be placed upside down on top of a sofa, anything to minimise items being placed back onto damp carpet. Really heavy items with small contact areas can also indent the carpet backing and underlay, that's why it is vital that furniture must be returned to their original position, on existing indents.
Dave.