ブラウザーツールボックスで調べればわかるでしょ
#treestyletab_piro_sakura_ne_jp-menuitem-_context_newTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_newGroup,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_separator\:afterNewTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_reloadTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_toggleMuteTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_pinTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_topLevel_toggleSticky,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_unloadTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_duplicateTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_separator\:afterDuplicate,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_bookmarkTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_moveTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_copyLinks,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_sendTabsToDevice,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_reopenInContainer,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_selectAllTabs,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_separator\:afterCollapseExpand,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_closeTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_closeDuplicatedTabs,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_closeMultipleTabs,
#treestyletab_piro_sakura_ne_jp-menuitem-_context_undoCloseTab,
#treestyletab_piro_sakura_ne_jp-menuitem-_separatprBeforetreestyletab,
#treestyletab_piro_sakura_ne_jp-menuitem-_treestyletab,
#context-sep-viewsource-commands {
display: none !important;
}