In Impress tables, if you want to select multiple cells by clicking the first cell, then holding the Shift key and then clicking the last cell simply doesn't work.

Steps to reproduce:
1) Create a blank Impress document
2) Insert a 5 x 5 table
3) Add any content to the table (I attached a sample table for testing)
4) Click the first cell (1, 1)
5) Hold the Shift key and click any other cell (f.i cell (3, 4))
6) Notice that the range from (1, 1) to (3, 4) will not be selected; instead only cell (3, 4) is selected

In Writer tables the procedure described above works as expected. Hence, the expected behavior in Impress should be the same.