Can parameters have dropdown list?

Yes. When you create a parameter, set Allowable values to List, and the control renders as a dropdown.

The list can be typed in by hand, pasted from a clipboard, or populated From Field, which reads the current values of a dimension.

The catch with From Field on a classic parameter is that it takes a snapshot. New members appearing in the data later will not be added, so the list drifts out of date silently. Dynamic parameters fix this by refreshing the list when the workbook opens.

The other options are All, which accepts any typed value, and Range, which gives a slider between a minimum and maximum.