Unforutnately, it does not show in your "XP Gain Rate".
It will still be as 100%. The only to know is by having the "Checked Shield" symbol: (or by killing a creature and calculating the exp... xD)
The experience bonus:
- 1 Voc: 20%
- 2 Voc: 30%
- 3 Voc: 60%
- 4 Voc: 100%
Note that, if your party has, for an example, 1 EK and 2 ED, you will get less exp than if it was 1 EK 1 ED, having 2 EDs doesn't increase the bonus, since it is still only 2 vocations inside the party.
There is a formula to calculate how much experience you will get from a creature:
M = Monster Exp
S = Shared Party Bonus
P = Amount of people in the party
C = Character exp gain rate (100% for normal exp, 150% for stamina, 225% for stamina + boost, etc...)
Source: https://tibia.fandom.com/wiki/Party#Sharing_Experience