Create permanent borders

I created a spreadsheet long ago for tracking my solar usage. Is there any way to make certain border lines permanent? I input dates and power usage/generation. I want the heavier green lines to NOT disappear when I copy something into the cell above the horizontal lines. I remember being able to do that somehow in Lotus 1-2-3, but don’t know if Excel had that capability.

I’m retired IT support, managed Win NT neworks for years, switched to XUbuntu 12+ yrs ago.

Running version 24.2.7.2 (X86_64)/

Here’s a link to the file:

https://help.libreoffice.org/latest/en-US/text/shared/01/pastespecialmenu.html?&DbPAR=CALC&System=WIN