🎩🎩🎩 𝐂𝐮𝐬𝐭𝐨𝐦 𝐏𝐨𝐰𝐞𝐫 𝐬𝐲𝐦𝐛𝐨𝐥𝐬 𝐢𝐧 𝐊𝐢𝐂𝐀𝐃
In a nutshell:
1️⃣ You need a custom Power symbol (for a ground or power domain).
2️⃣ Copy the existing generic symbol.
3️⃣ 🔴 Edit 𝗦𝘆𝗺𝗯𝗼𝗹 𝗻𝗮𝗺𝗲, 𝗦𝘆𝗺𝗯𝗼𝗹 𝘃𝗮𝗹𝘂𝗲 and 𝗣𝗶𝗻 𝗻𝗮𝗺𝗲 𝗼𝗳 𝘁𝗵𝗲 𝗽𝗮𝗿𝘁𝗶𝗰𝘂𝗹𝗮𝗿 𝗽𝗶𝗻.
Not everything is possible in #kicad, but what is possible is simple to do.
Custom power symbols in KiCAD