FreeOffice: The command Remove empty rows is not included in SoftMaker FreeOffice.
To delete all empty rows within a certain range of rows, select the range from which you want to remove empty rows.
Then choose the ribbon command Data | group Edit | Remove empty rows 
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PlanMaker scans this range for rows that are completely empty (i.e. where none of their cells contain a value). All corresponding rows are deleted.
Note
Normally, you select a range of complete rows before using this command. However, you can also select a cell range that doesn't consist of complete rows. PlanMaker will then ask you if you want it to delete the corresponding rows completely:
▪If your answer is Yes, all corresponding rows will be deleted completely.
▪If your answer is No, only cells within the selection will be deleted. The cells to the left and right of the selection will remain unchanged.