You can click Ctrl + Mouse Mid to copy a Command Block with its NBT. But I found that after I copied one which is activated with Lever, then destroyed this one and placed the copied one on the world, it never works even though it's "Always Active". I have to turn it into "Need Redstone" and active for a time then turn it back to "Always Active" and works normally.

How to Produce

1. Place a Repeat Command Block
2. Insert execute as @e[type=minecraft:evoker_fangs] at @s unless block ~ ~-1 ~ #minecraft:wither_immune run setblock ~ ~-1 ~ minecraft:reinforced_deepslate destroy
3. "Need Redstone", then active it with Lever on
4. Ctrl + Mouse Mid to copy, then destroy the Command Block when it's activated
5. Place the one you copied, set to "Always Active"
6. Summon Evoker Fangs

           The block without "#minecraft:wither_immune" and below the Fangs isn't replaced with Reinforced Deepslate.

       7. Turn to "Need Redstone"

       8. Active, the Command Block works

       9. Turn to "Always Active"

          The Command Block works normally.