Select the Partition, and select the corresponding Partition tab in the lefthand panel (This can be Parent Partition 1, Partition, etc. depending on the partition whose height you wish to change).

In the lefthand Properties panel the opens, select the Partition Dimensions dropdown menu.

Usually, the Partition Height field that opens up, will be auto-calculated and thus not editable. To edit the height, select Switch the Fixed Height (For this to work, the other partitions' height(s) should not be fixed as well, it should be set to auto-calculated. This is usually the case by default).

Type in the desired partition Height value into the Partition Height field.

Press Enter to save changes