https://wiki.documentfoundation.org/ReleaseNotes/5.4#Calc A new Cell Protection toggle command was added to Edit ▸ Cell Protection to change the protection status of the cell. tdf#95885 (Gülşah Köse) Four new sheet protection options have been added to optionally allow insertions and deletions of rows and columns. The Insert rows and Insert columns options allow row and column insertions even when the sheet is protected, whereas the Delete rows and Delete columns options allow row and column deletions. Note that when row and column insertions are enabled, you can insert rows or columns even when the range to insert the new rows or columns into contains protected cells which will get shifted after the insertion. Row and column deletions, on the other hand, are only allowed on unprotected cells. tdf#43535 (Kohei Yoshida, Collabora) These need to be documented in this page: https://help.libreoffice.org/latest/en-US/text/scalc/guide/cell_protect.html?DbPAR=CALC#bm_id3146119
Olivier Hallot committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/766e173ed8c9b3401c07fa26716eefe1b2430be5 tdf#141766 Update cell protection Help page