How can I delete individual line from table?

[ColdWater]

not delete entire row or cells but individual lines

[EarnestAl]

I presume you mean that you want to remove a border line between two cells.

1. select the two (or more) cells between which you want to remove the border
2. Right click and select Properties > Borders
3. Click twice on the border in the dialogue between the cells so it disappears. OK

[LeroyG]

LibreOffice Help on User Defined Borders in Text Documents.