Yes, there is indeed a way to bypass this. First of all, create another scoreboard objective that will be used as the dummy objective:
/scoreboard objectives add bossHealth_1 dummy
Now place a repeating command block containing the following command:
/scoreboard players operation Joe bossHealth = @e[type=Zombie,name=Joe] bossHealth_1
bossHealth objective in the sidebar as a scoreboard. Then, every time that you want to change the
bossHealth objective, change the
bossHealth_1 objective instead and the
bossHealth objective wil change automatically.
This is because the scoreboard operations command will change the first entity's specific score (the
Joe bossHealth part) according to the second entity's other specific score (the
@e[type=Zombie,name=Joe] bossHealth_1 part), by the operation provided (the
For more about the scoreboard operations command, click here and scroll to the bottom of the table.